Re: [Tutor] Hello!

[Joaquin Alzola]

> I don't know if i'm sending the email to the right address but here it goes!. 
> Would Python be a suitable language for first time learners like me?

I suppose it depends on each one but from my experience I try with C and then 
Java without finding the feeling for it ...

Then I learn python over a year ago and I can tell you that it is one of the 
best for first timers.

I am now learning Java and it is much easier after somehow controlling python.

(I suppose ruby has to be the same that python).

--
Joaquin
This email is confidential and may be subject to privilege. If you are not the 
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Re: [Tutor] Hello!

[Alan Gauld via Tutor]

On 09/09/16 17:21, Eric Gardner wrote:
> I don't know if i'm sending the email to the right address but here it
> goes!. Would Python be a suitable language for first time learners like me?

Yes, this is the right address, welcome.

And yes, Python is an excellent language with which to learn
programming. If you are comfortable with basic computer use
you can try my tutorial(see below) or there is a whole
web page on the Python site dedicated to new programmers:

http://wiki.python.org/moin/BeginnersGuide/NonProgrammers



-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


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[Tutor] Hello!

[Eric Gardner]

I don't know if i'm sending the email to the right address but here it
goes!. Would Python be a suitable language for first time learners like me?

-- 
Eric G
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Re: [Tutor] Hello everybody

[Joseph John]

On Mon, Jun 13, 2016 at 11:55 PM, Влад <79099012...@yandex.ru> wrote:

>Hi. I've just begin with Python? I'm 34. Is it late or what? If it is -
> I
>will cut it out. What you think guys?
>**
>
Here  myself 48 crossed, just started taking python step by step
Welcome to the herd


>--**
>** **,
>, PR- Rich PR
>+79099012930
>**
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Re: [Tutor] Hello everybody

[Alan Gauld via Tutor]

On 13/06/16 20:55, Влад wrote:
>Hi. I've just begin with Python? I'm 34. Is it late or what? If it is - I
>will cut it out. What you think guys?

No you are just a young whippersnapper.
I've had students use my tutorial in their 70s
(and in their pre-teens too)

But is this also your start in programming in general?
Or can you already program in any other language?
If the latter you will find python easy to pick up.

If the former you have some extra work to learn the
basic concepts as well as how Python implements
those concepts.

Finally, it will help if you are experienced in general
computer use: navigating folders, manipulating files (especially
to edit text files), using a command console, etc.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


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Re: [Tutor] Hello everybody

[Joel Goldstick]

On Mon, Jun 13, 2016 at 3:55 PM, Влад <79099012...@yandex.ru> wrote:
>Hi. I've just begin with Python? I'm 34. Is it late or what? If it is - I
>will cut it out. What you think guys?
>**
>--**
>** **,
>, PR- Rich PR
>+79099012930
>**
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You are an hour and a half too late!  Late for what?  welcome

-- 
Joel Goldstick
http://joelgoldstick.com/blog
http://cc-baseballstats.info/stats/birthdays
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[Tutor] Hello everybody

[Влад]

   Hi. I've just begin with Python? I'm 34. Is it late or what? If it is - I
   will cut it out. What you think guys?
   **
   --**
   ** **,
   , PR- Rich PR
   +79099012930
   **
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Re: [Tutor] Hello! Questions

[Marco Soldavini]

On Fri, Feb 19, 2016 at 3:32 PM, Peter Otten <__pete...@web.de> wrote:

>
>
> Also, after reading http://openopc.sourceforge.net/api.html I wonder if it
> wouldn't be better to go with the timestamp provided by the server
>
>   bool1.append(opc.read(".watchdog"))
>

yes but my next step is to load some of this data up to SQL and the
timestamp provided by the opc was difficult to manage into a TIME field. I
manage to insert the appended data instead with the timestamp generated
with my code.

I'll work more on that to see if it is possible to get the original
timestamp. I don't require high precision just something around the second
is ok.


>
> With a slight modification of Alan's suggestion you could write to a list
> of
> dicts instead of a dict of lists like so:
>
> # outside the loop
> WANTED = [".watchdog", ".analog1", ".analog2]
> data = []
>
> # in the loop:
>  data.append({r[0]:r[1:] for r in opc.read(WANTED)})
>
>
>
Thanks for the helpful hints. I have a ton of questions yet to come!

Marco
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Re: [Tutor] Hello! Questions

[Peter Otten]

Marco Soldavini wrote:

Random remarks about your code:

> #While loop - scanning and storing OPC values at scan rate
> while (abort == 0):

The loop continues to work if you change it to

while True:
 
> # ESC pressed?
> if msvcrt.kbhit() and ord(msvcrt.getch()) == 27:
> abort = 1
> break
> 
> # Server up
> if opc.ping():
> 
> 
> if opc['.run_batch'] == True and rec_started == False:

In idiomatic Python you don't compare boolean values, you test:

  if opc['.run_batch'] and not rec_started:

> # Setting arrays for variables
> bool1 = []
> ana1 = []
> ana2 = []
> ana3 = []
> ana4 = []
> rec_started = True
> 
> if opc['.run_batch'] == True and rec_started == True:
> # scan time
> time2 = time.time()
> dtime = time2 - time1
> 
> if dtime > 2 and comm_alarm == False:
> dt = datetime.datetime.now()
> bool1.append((opc.read('.watchdog')
[0],opc.read('.watchdog')[1],dt))

Invoking opc.read(".watchdog") twice looks wrong, the two values might be 
out of sync. I suspect that you want

  result = opc.read(".watchdog")
  bool1.append((result[0], result[1], dt))

Also, after reading http://openopc.sourceforge.net/api.html I wonder if it 
wouldn't be better to go with the timestamp provided by the server

  bool1.append(opc.read(".watchdog"))

With a slight modification of Alan's suggestion you could write to a list of 
dicts instead of a dict of lists like so:

# outside the loop
WANTED = [".watchdog", ".analog1", ".analog2]
data = []

# in the loop:
 data.append({r[0]:r[1:] for r in opc.read(WANTED)})

> ana1.append((opc.read('.analog2')[0],opc.read('.analog2')
[1],dt))
> time1 = time2
> 
> 
> else:
> # scan time
> time2 = time.time()
> dtime = time2 - time1
> if dtime > 2:
> print "ERROR: OPC Server is down”
> 


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Re: [Tutor] Hello! Questions

[Alan Gauld]

On 19/02/16 07:51, Marco Soldavini wrote:
> Sorry, Here my code in plaintext
> ...

thanks

>> Better is to use a dictionary with your "variables" 

>> data[keyName].append(value) 
> Ok so I will look more into dictionaries, it is like hash tables?

Exactly.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


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Re: [Tutor] Hello! Questions

[Marco Soldavini]

Sorry, Here my code in plaintext

#While loop - scanning and storing OPC values at scan rate
while (abort == 0):

    # ESC pressed?
    if msvcrt.kbhit() and ord(msvcrt.getch()) == 27:
        abort = 1
        break

    # Server up
    if opc.ping():


        if opc['.run_batch'] == True and rec_started == False:
            # Setting arrays for variables
            bool1 = []
            ana1 = []
            ana2 = []
            ana3 = []
            ana4 = []
            rec_started = True

        if opc['.run_batch'] == True and rec_started == True:
            # scan time
            time2 = time.time()
            dtime = time2 - time1

            if dtime > 2 and comm_alarm == False:
                dt = datetime.datetime.now()
                
bool1.append((opc.read('.watchdog')[0],opc.read('.watchdog')[1],dt))
                
ana1.append((opc.read('.analog2')[0],opc.read('.analog2')[1],dt))
                time1 = time2
                

    else:
        # scan time
        time2 = time.time()
        dtime = time2 - time1
        if dtime > 2:
            print "ERROR: OPC Server is down”



Il giorno 19 febbraio 2016 @ 02:18:05, Alan Gauld (alan.ga...@btinternet.com) 
ha scritto:
> Let's say I can have 30-40 variables (so 30-40 append instructions at every 
> cycle, with same scan rate). 

Its not clear what the scan rate actually is. 
How many scans per second? 


yes scan per second. For example a new fetch every 2 second, so a new append to 
array every 5 second



> shall run for 2 hours and gather let's say 2000 elements in 40 arrays, 
> could this be a problem in term of computation? 

Yes it could, but it depends on what size the data is. 
You need to do some basic math to calculate it out. 

40 * 2000 = 80k items. If they are integers then its 
4 bytes per item so 320Kbytes. Not too bad. If they 
are 100 character strings then its into MB but on a 
modern PC still not too bad. But if it's intended to 
run in an embedded controller with only 1M of RAM 
it might be a big issue. 


Pc for sure, I think with 8GB RAM. I’ll do some detailed calculations about 
that.

> Second question is I want the arguments in the opc.read command not to be 
> hard coded but coming from a configuration files. 

OK. You might want to think about what that file 
format would look like. 


I’d like to have an xml file or csv file to parse (another topic I wanna learn) 
and in this file I have a table defining my variables with a name and another 
field for description


> You see the names of my arrays? bool1, ana1, ana2, etc... Is it possible to 
> derive number and names of these variables from an external files. 

It is but its usually a bad idea. 
Better is to use a dictionary with your "variables" 
as keys and your arrays as values. So your append 
looks like 

data = dict() 
keyName = readFromFile() 
value = readFromFile() 

data[keyName].append(value) 
Ok so I will look more into dictionaries, it is like hash tables?





> Let's say in this configuration file I can say I have to read 10 arrays or 
> 20 arrays and then my program adjust the while cycle consequently. 

Yes that's doable. 

> Maybe an array of array where the second dimension is coming from the 
> config file. 

I'd use the dictionary approach rather than arrays of arrays. 
(Which are probably lists of lists in Python.) 


Thanks!
Marco
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Re: [Tutor] Hello! Questions

[Alan Gauld]

On 18/02/16 21:17, Marco Soldavini wrote:

> *# While loop - scanning and storing OPC values at scan rate 

**while *(abort == 0):
> 
> 
> *# ESC pressed? **if *msvcrt.kbhit() *and *ord(msvcrt.getch()) == 27:
> abort = 1
> 
> 

As you can see your code is all messed up.
You need to post in plain text format.

> Let's say I can have 30-40 variables (so 30-40 append instructions at every
> cycle, with same scan rate).

Its not clear what the scan rate actually is.
How many scans per second?

> Is this scalable when variables are getting bigger. 

The variables stay the same size it's the data that
gets bigger. But how scalable it is depends on how
much memory you have. And how fast your storage
devices are. And what else is running on your
system at the time.

> shall run for 2 hours and gather let's say 2000 elements in 40 arrays,
> could this be a problem in term of computation?

Yes it could, but it depends on what size the data is.
You need to do some basic math to calculate it out.

40 * 2000 = 80k items. If they are integers then its
4 bytes per item so 320Kbytes. Not too bad. If they
are 100 character strings then its into MB but on a
modern PC still not too bad. But if it's intended to
run in an embedded controller with only 1M of RAM
it might be a big issue.

> Second question is I want the arguments in the opc.read command not to be
> hard coded but coming from a configuration files.

OK. You might want to think about what that file
format would look like.

> You see the names of my arrays? bool1, ana1, ana2, etc... Is it possible to
> derive number and names of these variables from an external files.

It is but its usually a bad idea.
Better is to use a dictionary with your "variables"
as keys and your arrays as values. So your append
looks like

data = dict()
keyName = readFromFile()
value = readFromFile()

data[keyName].append(value)

> Let's say in this configuration file I can say I have to read 10 arrays or
> 20 arrays and then my program adjust the while cycle consequently.

Yes that's doable.

> Maybe an array of array where the second dimension is coming from the
> config file.

I'd use the dictionary approach rather than arrays of arrays.
(Which are probably lists of lists in Python.)


-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


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Re: [Tutor] Hello! Questions

[Marco Soldavini]

On Wed, Feb 17, 2016 at 11:13 AM, Alan Gauld 
 wrote:


> > My first question is about data types, data structures in general and how
> > to organize an efficient loop for recording data.
>
> > while (stop condition false)
> >read data
> >write data into local array or something
> >wait sample time
>
> That's a good start. What is the question?
> You say you know how to read data fro openopc, so the
> first loop line should be fine.
> Storing into a list involves the append method:
>
> myDataList.append(myData)
>
> and the wait will probably be openopc specific
> but if not you can use the time.sleep() function.
>
>
> hth
> --
> Alan G



Ok here my main loop for gathering data (stripped off some code to make it
easier to read):


*# While loop - scanning and storing OPC values at scan rate **while *(abort
== 0):


*# ESC pressed? **if *msvcrt.kbhit() *and *ord(msvcrt.getch()) == 27:
abort = 1


*break *
*# Server up **if *opc.ping():


*if *opc[*'.run_batch'*] == True *and *rec_started == False:

*# Setting arrays for variables *bool1 = []
ana1 = []
ana2 = []
ana3 = []
ana4 = []
rec_started = True

*if *opc[*'.run_batch'*] == True *and *rec_started == True:

*# scan time *time2 = time.time()
dtime = time2 - time1

*if *dtime > 2 *and *comm_alarm == False:
dt = datetime.datetime.now()
bool1.append((opc.read(*'.watchdog'*)[0],opc.read(
*'.watchdog'*)[1],dt))
ana1.append((opc.read(*'.analog2'*)[0],opc.read(*'.analog2'*
)[1],dt))
time1 = time2


*else*:

*# scan time *time2 = time.time()
dtime = time2 - time1
*if *dtime > 2:
*print **"ERROR: OPC Server is down"*



As you can see I am using append to store data from opc.read command which
returns elements of string array.

Let's say I can have 30-40 variables (so 30-40 append instructions at every
cycle, with same scan rate).

Is this scalable when variables are getting bigger. What if this program
shall run for 2 hours and gather let's say 2000 elements in 40 arrays,
could this be a problem in term of computation?


Second question is I want the arguments in the opc.read command not to be
hard coded but coming from a configuration files.


You see the names of my arrays? bool1, ana1, ana2, etc... Is it possible to
derive number and names of these variables from an external files.

Let's say in this configuration file I can say I have to read 10 arrays or
20 arrays and then my program adjust the while cycle consequently.


Maybe an array of array where the second dimension is coming from the
config file.


Is this clear?


Version of python is 2.7.9 running on Windows 7.


Cheers,

Marco
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[Tutor] Hello! Questions

[Marco Soldavini]

Hi,
I am almost new to python and I am trying to build a not so easy app (but
very neat and useful) related to industrial automation.

Is this the right place to knock down problems one by one?
Basically my app has several interactions but the most important is reading
values from an embedded machine (better a PLC) via the OPC protocol.

I already tested this with some values of various kind (real, boolean,
strings). Basically each tag is read with a fixed sample time from a stream
opened in OPC and recorded onto an array in python.

Is it better I explain you the main picture? I am not here for spoon
feeding but just tips and suggestion and maybe solution to particular
problems I might find on the track.

Something about OPC is here: https://opcfoundation.org/about/what-is-opc/

The lib I am using is openopc.

My first question is about data types, data structures in general and how
to organize an efficient loop for recording data.

Basically something like

while (stop condition false)
read data
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[Tutor] Hello! Questions

[Marco Soldavini]

I hit the send button too early. anyway

Basically something like

while (stop condition false)
read data
write data into local array or something
wait sample time


Thanks
marco
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[Tutor] hello.

[Lolo Lolo]

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Re: [Tutor] Hello, and a newbie question

[Prasad, Ramit]

eryksun wrote:
 On Tue, Apr 16, 2013 at 7:57 PM, Virgilio Rodriguez Jr
 virgiliorodrigue...@gmail.com wrote:
  Can someone please do me the favor and remove me from this god forsaken
  email list I am sorry I signed up all it has done is taken over my phone and
  rings all night long with emails I am not interested in any more because it
  is just too many darn emails. I keep trying to log in and nothing it will
  not let me unsubscribe and it is BS already.
 
 You can get a password reminder here:
 http://mail.python.org/mailman/options/tutor
 
 If you're sure that you have the correct password and still can't
 unsubscribe, then email the administrator, tutor-ow...@python.org.
 Alan Gauld is active in this thread, BTW, in case you happen to have
 read the admin page where it says Tutor list run by wescpy at
 gmail.com, alan.gauld at btinternet.com.

Or switch to digest mode which will email once a day with all the 
messages in it. Be glad you are not subscribed to the main Python 
mailing list as it is far more active than the tutor list. ;)


~Ramit


This email is confidential and subject to important disclaimers and
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[Tutor] Hello, and a newbie question

[Andy McKenzie]

Hey folks.

I'm just starting to pick up Python, and I'd like to avoid some of the
mistakes I made in the past.  To elaborate on that, my primary
programming/scripting experience is PHP, with a little bit of Perl thrown
in.  Like so many people who write in PHP, I was entirely self-taught, and
would be the first to admit that a lot of what I've written is, well...
wrong.  It works, but it's sloppy and inefficient, because there were
standard constructions and solutions I just didn't know about.  I'd like to
avoid that with Python.

So:  my first two questions to the list.

1) Python 2.7 or 3.x?  I know I'm going to want to do some work with NLTK
(which appears to only have an alpha version out for Python 3), but I've
just gone through the hassle of dealing with an upgrade from PHP 4 to 5.3,
and I'd rather not start learning something that's already obsolete.  Any
words of advice?

2) Best practices.  I have the WROX Press Beginning Python book, which
targets Python 2.  Clearly that's of only limited value if I'm going to go
with Python 3, but it looks like it's at least going to be a good overview.
 But some of the stuff they do seems to be fairly personalized, rather than
trying to follow standards.  Should I just start out with the tutorial from
docs.python.org?  I would assume that that would start putting me in the
right habits from the beginning... is that accurate, or is there a better
way to go?

Thanks in advance,
  Andy McKenzie
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Re: [Tutor] Hello, and a newbie question

[Alan Gauld]

On 16/04/13 16:58, Andy McKenzie wrote:


1) Python 2.7 or 3.x?  I know I'm going to want to do some work with
NLTK (which appears to only have an alpha version out for Python 3), but
I've just gone through the hassle of dealing with an upgrade from PHP 4
to 5.3, and I'd rather not start learning something that's already
obsolete.  Any words of advice?


Upgrading from P2 to P3 is not too onerous but there will be some 
changes to make at some po9nt.
However P2 is the one to go for if you want to do anything industrial 
just now because not all the 3rd party libraries (like NLTK) are fully 
ported to v3 yet, including some pretty significant ones.


OTOH If you are only experimenting/learning then going with P3 will 
avoid any relearning in the future.



2) Best practices.  I have the WROX Press Beginning Python book,


Sorry, I've never even seen that one so can't comment...


http://docs.python.org?  I would assume that that would start putting
me in the right habits from the beginning... is that accurate,


Yes, for existing programmers new to Python the official tutor is nearly 
always the best place to start. You can fill in the gaps elsewhere 
later. And the tutor is pretty short and fast paced, you can just about 
get through it all in an afternoon - certainly in a day.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] Hello, and a newbie question

[Dave Angel]

On 04/16/2013 11:58 AM, Andy McKenzie wrote:

Hey folks.

I'm just starting to pick up Python, and I'd like to avoid some of the
mistakes I made in the past.  To elaborate on that, my primary
programming/scripting experience is PHP, with a little bit of Perl thrown
in.  Like so many people who write in PHP, I was entirely self-taught, and
would be the first to admit that a lot of what I've written is, well...
wrong.  It works, but it's sloppy and inefficient, because there were
standard constructions and solutions I just didn't know about.  I'd like to
avoid that with Python.



Welcome to the mailing list.  I expect you'll find Python a much cleaner 
language than the other two, though php has some definite convenience 
for its particular niche.





So:  my first two questions to the list.

1) Python 2.7 or 3.x?  I know I'm going to want to do some work with NLTK
(which appears to only have an alpha version out for Python 3), but I've
just gone through the hassle of dealing with an upgrade from PHP 4 to 5.3,
and I'd rather not start learning something that's already obsolete.  Any
words of advice?



If you have to use a library that's not available yet for 3.x, then you 
need to use 2.x  on the other hand, if you're learning now, maybe that 
library will be available by the time you actually need it.


For most people, I'd advise against trying to use a tutorial that 
targets a different version than you're running.  If you get frustrated 
quickly, you can get bogged down by the differences when you're just 
copying an exact program out of some book.


Python 3 in particular has spent some substantial effort cleaning up the 
warts, the biggest one being Unicode.  For beginning programmers using 
only ASCII, probably the main thing that'll bog you down is that print() 
is now a function, rather than a statement, so you need parentheses. 
But once you get used to seeing syntax error, you quickly get the hang 
of it.  And once you do, the function is much nicer.




2) Best practices.  I have the WROX Press Beginning Python book, which
targets Python 2.  Clearly that's of only limited value if I'm going to go
with Python 3, but it looks like it's at least going to be a good overview.
  But some of the stuff they do seems to be fairly personalized, rather than
trying to follow standards.  Should I just start out with the tutorial from
docs.python.org?  I would assume that that would start putting me in the
right habits from the beginning... is that accurate, or is there a better
way to go?

Thanks in advance,
   Andy McKenzie


I'd start with the python.org tutorial for the version you're trying to 
learn.  Get serious about trying everything, and don't try to absorb it 
all in one sitting, even though it can be done.


And use a text editor that helps you indent, or even that colorizes your 
code.  And when you just want to try things, use the interpreter 
directly.  It's amazing what you can learn directly from it.  You can 
ask the interpreter lots of questions about an object:


   help(obj)
   dir(obj)
   print( type(obj) )
   print( repr(obj) )

And don't forget to post here when you seem to be stuck.  Sometimes a 
well placed comment beats days of struggling.  When you do get an 
exception you don't understand, paste the whole thing, as well as the 
code you were trying.


Best of luck.



--
DaveA
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Re: [Tutor] Hello, and a newbie question

[Andy McKenzie]

On Tue, Apr 16, 2013 at 4:18 PM, Dave Angel da...@davea.name wrote:

 On 04/16/2013 11:58 AM, Andy McKenzie wrote:

 Hey folks.

 I'm just starting to pick up Python, and I'd like to avoid some of the
 mistakes I made in the past.  To elaborate on that, my primary
 programming/scripting experience is PHP, with a little bit of Perl thrown
 in.  Like so many people who write in PHP, I was entirely self-taught, and
 would be the first to admit that a lot of what I've written is, well...
 wrong.  It works, but it's sloppy and inefficient, because there were
 standard constructions and solutions I just didn't know about.  I'd like
 to
 avoid that with Python.


 Welcome to the mailing list.  I expect you'll find Python a much cleaner
 language than the other two, though php has some definite convenience for
 its particular niche.




  So:  my first two questions to the list.

 1) Python 2.7 or 3.x?  I know I'm going to want to do some work with NLTK
 (which appears to only have an alpha version out for Python 3), but I've
 just gone through the hassle of dealing with an upgrade from PHP 4 to 5.3,
 and I'd rather not start learning something that's already obsolete.  Any
 words of advice?


 If you have to use a library that's not available yet for 3.x, then you
 need to use 2.x  on the other hand, if you're learning now, maybe that
 library will be available by the time you actually need it.

 For most people, I'd advise against trying to use a tutorial that targets
 a different version than you're running.  If you get frustrated quickly,
 you can get bogged down by the differences when you're just copying an
 exact program out of some book.

 Python 3 in particular has spent some substantial effort cleaning up the
 warts, the biggest one being Unicode.  For beginning programmers using only
 ASCII, probably the main thing that'll bog you down is that print() is now
 a function, rather than a statement, so you need parentheses. But once you
 get used to seeing syntax error, you quickly get the hang of it.  And once
 you do, the function is much nicer.



  2) Best practices.  I have the WROX Press Beginning Python book, which
 targets Python 2.  Clearly that's of only limited value if I'm going to go
 with Python 3, but it looks like it's at least going to be a good
 overview.
   But some of the stuff they do seems to be fairly personalized, rather
 than
 trying to follow standards.  Should I just start out with the tutorial
 from
 docs.python.org?  I would assume that that would start putting me in the
 right habits from the beginning... is that accurate, or is there a better
 way to go?

 Thanks in advance,
Andy McKenzie


 I'd start with the python.org tutorial for the version you're trying to
 learn.  Get serious about trying everything, and don't try to absorb it all
 in one sitting, even though it can be done.

 And use a text editor that helps you indent, or even that colorizes your
 code.  And when you just want to try things, use the interpreter directly.
  It's amazing what you can learn directly from it.  You can ask the
 interpreter lots of questions about an object:

help(obj)
dir(obj)
print( type(obj) )
print( repr(obj) )

 And don't forget to post here when you seem to be stuck.  Sometimes a well
 placed comment beats days of struggling.  When you do get an exception you
 don't understand, paste the whole thing, as well as the code you were
 trying.

 Best of luck.




Thanks for the advice, folks.  Given that it looks like the biggest changes
are unicode handling (which I'm not going to need any time soon) and the
way the print function works, I decided to stick with 2.7.  I'm an IT guy,
though unemployed at the moment, and it occurred to me that I'm familiar
with Python, but not the version your entire established codebase is in
wasn't a great thing to have on a resume.

Since it looks like the new formatting for print -- that is, print(Print
this stuff!) -- works fine in 2.7, I'm just getting myself used to doing
that from the beginning.

I went through the first four or five sections of the tutorial this
afternoon, with a few side trips into things that got me interested, and I
figure I'll do at least one more section after dinner.  I did find it
interesting that one of the first things I wanted to know turned out to be
an extremely common question:  What's the Python equivalent to print_r()
from PHP?  If any of you are familiar with PHP (I know at least a couple
of you seemed to be), you'll know that pprint() (which seems to be the most
common answer) isn't actually very close.  Its output isn't nearly as
readable.

For instance:  output of running print_r on a very short dictionary from
PHP:

Array
(
[key3] = thing3
[key2] = thing2
[key1] = thing1
)

And running pprint on the same dict in Python:

{'key1': 'thing1', 'key2': 'thing2', 'key3': 'thing3'}


I finally decided that a good project would be building a quick function
that recreates the print_r 

Re: [Tutor] Hello, and a newbie question

[Dave Angel]

On 04/16/2013 05:20 PM, Andy McKenzie wrote:




SNIP




Thanks for the advice, folks.  Given that it looks like the biggest changes
are unicode handling (which I'm not going to need any time soon) and the
way the print function works, I decided to stick with 2.7.  I'm an IT guy,
though unemployed at the moment, and it occurred to me that I'm familiar
with Python, but not the version your entire established codebase is in
wasn't a great thing to have on a resume.

Since it looks like the new formatting for print -- that is, print(Print
this stuff!) -- works fine in 2.7, I'm just getting myself used to doing
that from the beginning.



The degenerate print, where you're printing exactly one thing, works the 
same.  But if you have two things to print, putting parens around them 
in Python 2.x will cause a tuple to be printed, rather than printing the 
two with a space between.


 print(3,5)  -- version 2.x
(3, 5)

 print(3,5)  -- version 3.x
3 5

To get 3.x functionality, you'd want to use
from __future__ import print_function

and I do not think that works in 2.6 or older versions.  It also can be 
awkward even in 2.7 if you're mixing existing code with new print functions.




--
DaveA
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Re: [Tutor] Hello, and a newbie question

[Andy McKenzie]

On Tue, Apr 16, 2013 at 5:31 PM, Dave Angel da...@davea.name wrote:

 On 04/16/2013 05:20 PM, Andy McKenzie wrote:



  SNIP



  Thanks for the advice, folks.  Given that it looks like the biggest
 changes
 are unicode handling (which I'm not going to need any time soon) and the
 way the print function works, I decided to stick with 2.7.  I'm an IT guy,
 though unemployed at the moment, and it occurred to me that I'm familiar
 with Python, but not the version your entire established codebase is in
 wasn't a great thing to have on a resume.

 Since it looks like the new formatting for print -- that is, print(Print
 this stuff!) -- works fine in 2.7, I'm just getting myself used to doing
 that from the beginning.


 The degenerate print, where you're printing exactly one thing, works the
 same.  But if you have two things to print, putting parens around them in
 Python 2.x will cause a tuple to be printed, rather than printing the two
 with a space between.

  print(3,5)  -- version 2.x
 (3, 5)

  print(3,5)  -- version 3.x
 3 5

 To get 3.x functionality, you'd want to use
 from __future__ import print_function

 and I do not think that works in 2.6 or older versions.  It also can be
 awkward even in 2.7 if you're mixing existing code with new print functions.


That's good to know, since I hadn't run into it yet.

So am I correct in understanding that I can just put the from __future__
import print_function in each new 2.7 script, and get identical
functionality to what happens in 3.x?  Or do I need to do that system-wide
somehow?

-Andy
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Re: [Tutor] Hello, and a newbie question

[Dave Angel]

On 04/16/2013 05:47 PM, Andy McKenzie wrote:

On Tue, Apr 16, 2013 at 5:31 PM, Dave Angel da...@davea.name wrote:


SNIP

To get 3.x functionality, you'd want to use
 from __future__ import print_function

and I do not think that works in 2.6 or older versions.  It also can be
awkward even in 2.7 if you're mixing existing code with new print functions.



That's good to know, since I hadn't run into it yet.

So am I correct in understanding that I can just put the from __future__
import print_function in each new 2.7 script, and get identical
functionality to what happens in 3.x?  Or do I need to do that system-wide
somehow?



Someone else may know if identical has some exceptions.  But as for 
where to put it, you'd need it for any module (including your own 
script) which is going to use the newer print() function.


And the nice thing is that the from-future directive is ignored in 3.x, 
so you don't have to remove it when you do progress.


--
DaveA
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Re: [Tutor] Hello, and a newbie question

[Alan Gauld]

On 16/04/13 22:20, Andy McKenzie wrote:


For instance:  output of running print_r on a very short dictionary from
PHP:

Array
(
 [key3] = thing3
 [key2] = thing2
 [key1] = thing1
)

And running pprint on the same dict in Python:

{'key1': 'thing1', 'key2': 'thing2', 'key3': 'thing3'}


I finally decided that a good project would be building a quick function
that recreates the print_r function, and I got that working.  New
function output, in Python:

(
 [key3] = thing3
 [key2] = thing2
 [key1] = thing1
)



You should probably use {} instead of () as the delimiter to indicate 
that the thing is a dictionary and not a tuple. but otherwise that's a 
good starter project.



--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] Hello, and a newbie question

[eryksun]

On Tue, Apr 16, 2013 at 6:17 PM, Dave Angel da...@davea.name wrote:
 Someone else may know if identical has some exceptions.  But as for where
 to put it, you'd need it for any module (including your own script) which is
 going to use the newer print() function.

I think any differences will result from the I/O system redesign in
3.x. In 2.x sys.stdout is still the old file type, which is
basically a wrapper around CRT FILE streams, while in 3.x it's a
TextIOWrapper wrapping a BufferedWriter wrapping a FileIO object.

Off the top of my head I don't have a clear example where it matters.
I vaguely recall having an issue with the default buffer flushing not
being the same. I think I was simulating scrolling text by printing a
carriage return ('\r') to overwrite a line. IRRC, in the end I opted
to directly use sys.stdout.write() and sys.stdout.flush().

Since __future__ imports are compiler directive, you have to include
them at the top of every module. print_function works in 2.6+. If
you just want the function under a different name, you can grab it
from the __builtin__ module:

 import __builtin__
 printf = getattr(__builtin__, 'print')
 printf('spam')
spam
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Re: [Tutor] Hello, and a newbie question

[Andy McKenzie]

On Tue, Apr 16, 2013 at 7:39 PM, Alan Gauld alan.ga...@btinternet.comwrote:

 On 16/04/13 22:20, Andy McKenzie wrote:

  For instance:  output of running print_r on a very short dictionary from
 PHP:

 Array
 (
  [key3] = thing3
  [key2] = thing2
  [key1] = thing1
 )

 And running pprint on the same dict in Python:

 {'key1': 'thing1', 'key2': 'thing2', 'key3': 'thing3'}


 I finally decided that a good project would be building a quick function
 that recreates the print_r function, and I got that working.  New
 function output, in Python:

 (
  [key3] = thing3
  [key2] = thing2
  [key1] = thing1
 )



 You should probably use {} instead of () as the delimiter to indicate that
 the thing is a dictionary and not a tuple. but otherwise that's a good
 starter project.


Good idea.  I went with () because I was just trying to duplicate the
output in PHP.  Now that I've got that, I can start thinking about
improvements.  Varying the punctuation to match the type would probably be
a good idea.

Thanks,
  Andy
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Re: [Tutor] Hello, and a newbie question

[Steven D'Aprano]

On 17/04/13 01:58, Andy McKenzie wrote:


1) Python 2.7 or 3.x?  I know I'm going to want to do some work with NLTK
(which appears to only have an alpha version out for Python 3), but I've
just gone through the hassle of dealing with an upgrade from PHP 4 to 5.3,
and I'd rather not start learning something that's already obsolete.  Any
words of advice?


Python 3.3 is awesome and much cleaner and better than 2.7, and 2.7 is
pretty damn good! So if you have a choice, pick 3.3. It's the future of
Python, 2.7 is the past.

But, 2.7 is still good, and if you need NLTK *right now* you might not have
a choice. (Unless you like being a guinea pig working with an alpha version.)

Also, the *incompatibilities* between 2.7 and 3.3 are fairly small. The
biggest difference from a beginner's perspective is that print is no longer
a statement, it is a function, so instead of writing this:

print Hello world!

you have to write this:

print(Hello world!)

That doesn't seem too onerous, does it? If you can cope with a few differences
of that complexity, why not learn both?



2) Best practices.  I have the WROX Press Beginning Python book, which
targets Python 2.  Clearly that's of only limited value if I'm going to go
with Python 3, but it looks like it's at least going to be a good overview.
  But some of the stuff they do seems to be fairly personalized, rather than
trying to follow standards.  Should I just start out with the tutorial from
docs.python.org?  I would assume that that would start putting me in the
right habits from the beginning... is that accurate, or is there a better
way to go?


If there's a Python 3 version of Learning Python, from O'Reilly Books (sorry
I forget the authors), give it a go. The first edition, at least, is an awesome
book although you will want a more recent version since the first edition
deals with Python 1.5, which truly is ancient history!

I haven't done the official Python tutorial, but from what I've seen of it,
it's pretty good.



--
Steven
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Re: [Tutor] Hello, and a newbie question

[eryksun]

On Tue, Apr 16, 2013 at 7:57 PM, Virgilio Rodriguez Jr
virgiliorodrigue...@gmail.com wrote:
 Can someone please do me the favor and remove me from this god forsaken
 email list I am sorry I signed up all it has done is taken over my phone and
 rings all night long with emails I am not interested in any more because it
 is just too many darn emails. I keep trying to log in and nothing it will
 not let me unsubscribe and it is BS already.

You can get a password reminder here:
http://mail.python.org/mailman/options/tutor

If you're sure that you have the correct password and still can't
unsubscribe, then email the administrator, tutor-ow...@python.org.
Alan Gauld is active in this thread, BTW, in case you happen to have
read the admin page where it says Tutor list run by wescpy at
gmail.com, alan.gauld at btinternet.com.
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Re: [Tutor] Hello, and a newbie question

[eryksun]

On Tue, Apr 16, 2013 at 8:15 PM, eryksun eryk...@gmail.com wrote:
 Can someone please do me the favor and remove me from this god forsaken
 email list I am sorry I signed up all it has done is taken over my phone and
 rings all night long with emails I am not interested in any more because it
 is just too many darn emails. I keep trying to log in and nothing it will
 not let me unsubscribe and it is BS already.

 You can get a password reminder here:
 http://mail.python.org/mailman/options/tutor

 If you're sure that you have the correct password and still can't
 unsubscribe, then email the administrator, tutor-ow...@python.org.
 Alan Gauld is active in this thread, BTW, in case you happen to have
 read the admin page where it says Tutor list run by wescpy at
 gmail.com, alan.gauld at btinternet.com.

I just went through the steps. You don't even need your password.
Enter your email address in the bottom field of the list info page:

http://mail.python.org/mailman/listinfo/tutor

Click the button that says Unsubscribe or edit options. Then simply
click the Unsubscribe button in the middle of the options page.
You'll get a confirmation email with instructions to complete the
process.
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Re: [Tutor] Hello, and a newbie question

[Sander Sweers]

On 04/17/2013 02:34 AM, eryksun wrote:
 I just went through the steps. You don't even need your password.
 Enter your email address in the bottom field of the list info page:
 
 http://mail.python.org/mailman/listinfo/tutor
 
 Click the button that says Unsubscribe or edit options. Then simply
 click the Unsubscribe button in the middle of the options page.
 You'll get a confirmation email with instructions to complete the
 process.

Or send an e-mail to tutor-requ...@python.org with unsubscribe in the
subject.

~sander
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Re: [Tutor] Hello Can someone looked at my problem? stuck

[Walter Prins]

On 3 October 2012 04:39, Palice Fan magicwizards...@gmail.com wrote:

 Hello
 i got stuck with the last bit of my programming practice.
 Can somebody help me?
 Write a program to read through a mail log, and figure out who had the most
 messages in the file. The program looks for “From” lines and takes the
 second parameter on
 those lines as the person who sent the mail.
 The program creates a Python dictionary that maps the sender’s address to
 the total number of
 messages for that person.
 After all the data has been read the program looks through the dictionary
 using a maximum loop
 (see Section 5.7.2) to find who has the most messages and how many
 messages the person has.

 Enter a file name: mbox-short.txt
 c...@iupui.edu :5
 Enter a file name: mbox.txt
 zq...@umich.edu :195

 Instead of printing off a number beside the email, i got another email and
 i dont know how to fix it.


For future reference, please either include the source code in the email as
text or as text attachment.  A screen capture means I have to retype all
your code (and in this case some data) in order to have a look at your
problem.  Not fun.

To fix your problem you have to reverse engineer what's going on in your
program.  I'll try and walk you through a little thought process in
figuring out what's going on to try and help you.

The last statement in your program (which is where the error is apparent)
prints a fixed email address followed by a value that's assigned earlier on
in a loop from the values variable. Consequently you should carefully
inspect your code and ask yourself how it's possible that an email address
instead of a number is being assigned to the values variable and thereby
eventually to the max variable.  (By the way, note that max is not
recommended as a variable name since max is also a built-in function in
Python and so by declaring a variable with the same name you're hiding
(known as shadowing) the Python function.  You can see there's something
special about it by the fact that IDLE colours it purple, which should tip
you off.)  But anyway, back to your max variable and values variable,
we now look back carefully at the loop to see how or where we might be
picking up email addresses when we should be getting integer counts...
Let's look carefully at the loop declaration:

for values in messages:

Hmmm, this is looping directly over the dictionary messages.  What is
returned when you iterate directly over a dict like that?  (Hint, it's not
the values, but the keys... e.g. the email addresses.)  Add some print
statements in your loop so you can see what happens when it runs, for
example:

print 'Starting iterating over messages dict'
for values in messages:
print 'Value of values this iteration =', values
if max is None or values  max:
print 'Updating max...'
max = values
print 'Value of max after this iteration =', max

If you apply similar changes to your program and run that you'll see why
the program doesn't work -- values is being assigned the keys (email
addresses) from the dict, not the values.  It should also become clear that
basically values is also a bad choice for the items being iterated over
in the messages dict and is perhaps adding to the confusion, better would
be:

for email_sender in messages:

This would make it clear that the items being iterated over are in fact the
email addresses.  It's always a good idea to use descriptive specific names
in your programs, not least because you yourself also need to read and
understand your own code.  Anyway, then later in your loop it's then
obvious that you can't just do:

if max is None or values  max:
max = values

(or if we use my suggested renaming)

if max is None or email_sender  max:
max = email_sender

Instead you want to retrieve the actual value (count) from the dict for
that specific email sender, e.g.

if max is None or messages[email_sender]  max:
max = messages[email_sender]

... and with that I've now basically explained the essence of your first
main problem.

However there remains another major flaw. Why are we assigning and
outputting 'c...@iupui.edu' as the email address with the maximum number of
emails, for any input?  Clearly that can't be right - if the input changes
and another email address has the highest count then this code will output
the wrong result.  So in addition to saving the max count, you must also
save the max sender in the loop.  I think that's enough for now, see if you
can fix your program given the above hints and if not post back again.

HTH,

Walter
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Re: [Tutor] hello

[Mark Lawrence]

On 17/09/2012 20:21, Fation Beqirllari wrote:

I have a php code and I want to translate it to python..Can you help me

please,or show me how to do it ?




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A better subject would help and no, we don't show you how to do it.  You 
show us that you'd made some sort of attempt at translating the code and 
run into a problem, then we'll help.


--
Cheers.

Mark Lawrence.

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[Tutor] Hello Python Tutor - help please!

[Ron Painter]

Hi, Cecilia:

I came across your posts when catching up with my tutor-request digest
emails. I did not see the Udacity site mentioned--if it was, my apologies
for the repetition.

Udacity.com, a free online education service, offers a number of
high-quality courses. They include interactive quizzes using code
sandboxes. The courses are 7 weeks long with online office hours and
forums. If you do not want to wait for the next start date, you can take
the courses online without getting instructor responses to students' posts.

Free Interactive Computer Courses (interaction via online quizzes using
code sandboxes):
http://www.udacity.com/

Intro to Computer Science
Python -- Beginner -- Project create functional search engine
http://www.udacity.com/view#Course/cs101/CourseRev/apr2012/Unit/671001/Nugget/675002

Programming Languages
Python, JavaScript -- Intermediate -- Project: Build a Functional Web
Browser
http://www.udacity.com/view#Course/cs262/CourseRev/apr2012/Unit/3001/Nugget/5001

Web Application Engineering
Python -- Intermediate -- Project: Build a Functional Blog
http://www.udacity.com/view#Course/cs253/CourseRev/apr2012/Unit/4001/Nugget/5002

Other courses available.

Best regards,
Ron Painter
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[Tutor] Hello Python Tutor - help please!

[Cecilia Chavana-Bryant]

Dear all,

I am just returning to my doctoral studies after a 7-month medical leave and 
desperately trying to catch up for lost time. I am COMPLETELY new to 
programming, well, I did try learning C for 3 weeks 3 yrs ago (with very little 
success) but had to stop and then spent 2 years in the Amazon climbing trees 
(lots more enjoyable than learning to programme!) and collecting loads of field 
data that I now need to post-process and analyse. By the way, the 3 weeks I 
spent trying to learn C really ended up being spent trying to get to grips with 
using a terminal for the first time in my life.

Since getting back to work, I was advised to try learning Python instead of C 
as it is a much easier first language to learn. I have been trying, but again, 
to not great success. I started following A Primer on Scientific programming 
with Python but I kept getting lost and stuck, specially on the exercises. I 
have also been advised that I should not try to learn programming by following 
guides but by trying to write the programmes I need to analyse my data. 
Although I can understand the logic behind this last bit of advise (it gives 
context and direction to the learning process) I have also gotten stuck trying 
this approach as I do not know how to programme!. Thus, I was hoping that 
some of you can remember how you got started and point me towards any really 
good interactive learning guides/materials and/or have a good learning strategy 
for a complete beginner. I have searched the web and was overwhelmed by choice 
of tutorials and guides. I have skimmed through a couple of tutorials but then 
fail to see how all that relates to my own work and I get stuck with what seems 
like basic important concepts so I don't progress. I then think I should try to 
make some progress with my own data analysing and go back to trying to learn to 
write a programme for my specific needs and get stuck again because this 
requires more advanced skills then the basic programming concepts I have been 
reading about on the learning guides. So, I am now feeling VERY frustrated and 
have no idea what on Earth I am doing! Can anyone please offer guidance in my 
learning process? I don't know how and what I should be spending my time 
learning first and/or if I should focus my learning towards the skill areas I 
will require to write my specific programmes, although I have no idea what 
these are. I would like advise on finding some really good interactive(let you 
know if your solution to an exercise is correct or not) and or video tutorials 
that give you feedback on the solutions you write to exercises.

Many thanks in advance for all your help, it will be much appreciated!



Cecilia Chavana-Bryant
DPhil Candidate - Remote sensing and tropical phenology
Environmental Change Institute
School of Geography and the Environment
University of Oxford
South Parks Road, Oxford, OX1 3QY
Web: http://www.eci.ox.ac.uk/teaching/doctoral/chavanabryantcecilia.php
Tel Direct: +44 (0)1865 275861
Fax: +44 (0)1865 275885
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Re: [Tutor] Hello Python Tutor - help please!

[Mario Cacciatore]

Hello,

My highest recommendation for you is to start with a simple hello world
program. Study that program, each line. Think about how and most
importantly, why it works.

Then, extend on it. Make it write to a file instead of a terminal. Then
make it read from a file and print to the terminal. Then make it print one
letter to each file, then read them back in and reconstruct the sentence.

Just take it slow, and one step at a time. So many times people simply go
for complex solutions and get lost in the complexity.

Sorry for top posting. My phone client doesn't support inline replies.

-Mario
--
From: Cecilia Chavana-Bryant
Sent: 8/22/2012 6:35 AM
To: tutor@python.org
Subject: [Tutor] Hello Python Tutor - help please!

   Dear all,

 I am just returning to my doctoral studies after a 7-month medical leave
and desperately trying to catch up for lost time. I am COMPLETELY new to
programming, well, I did try learning C for 3 weeks 3 yrs ago (with very
little success) but had to stop and then spent 2 years in the Amazon
climbing trees (lots more enjoyable than learning to programme!) and
collecting loads of field data that I now need to post-process and analyse.
By the way, the 3 weeks I spent trying to learn C really ended up being
spent trying to get to grips with using a terminal for the first time in my
life.

 Since getting back to work, I was advised to try learning Python instead
of C as it is a much easier first language to learn. I have been trying,
but again, to not great success. I started following A Primer on
Scientific programming with Python but I kept getting lost and stuck,
specially on the exercises. I have also been advised that I should not try
to learn programming by following guides but by trying to write the
programmes I need to analyse my data. Although I can understand the logic
behind this last bit of advise (it gives context and direction to the
learning process) I have also gotten stuck trying this approach as I do
not know how to programme!. Thus, I was hoping that some of you can
remember how you got started and point me towards any really good
interactive learning guides/materials and/or have a good learning strategy
for a complete beginner. I have searched the web and was overwhelmed by
choice of tutorials and guides. I have skimmed through a couple of
tutorials but then fail to see how all that relates to my own work and I
get stuck with what seems like basic important concepts so I don't
progress. I then think I should try to make some progress with my own data
analysing and go back to trying to learn to write a programme for my
specific needs and get stuck again because this requires more advanced
skills then the basic programming concepts I have been reading about on the
learning guides. So, I am now feeling VERY frustrated and have no idea what
on Earth I am doing! Can anyone please offer guidance in my learning
process? I don't know how and what I should be spending my time learning
first and/or if I should focus my learning towards the skill areas I will
require to write my specific programmes, although I have no idea what these
are. I would like advise on finding some really good interactive(let you
know if your solution to an exercise is correct or not) and or video
tutorials that give you feedback on the solutions you write to exercises.

 Many thanks in advance for all your help, it will be much appreciated!



Cecilia Chavana-Bryant
DPhil Candidate - Remote sensing and tropical phenology
Environmental Change Institute
School of Geography and the Environment
University of Oxford
South Parks Road, Oxford, OX1 3QY
Web: http://www.eci.ox.ac.uk/teaching/doctoral/chavanabryantcecilia.php
Tel Direct: +44 (0)1865 275861
Fax: +44 (0)1865 275885
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Re: [Tutor] Hello Python Tutor - help please!

[leon zaat]

If you don't have any prior programmers skills, i would advice first to learn 
the basics. You will need a good foundation, before it is possible to create 
complex functions.
Starting with complex functions is only frustrating if you don't understand the 
basics. 

From: cecilia.chavana-bry...@ouce.ox.ac.uk
To: tutor@python.org
Date: Wed, 22 Aug 2012 10:10:46 +
Subject: [Tutor] Hello Python Tutor - help please!







Dear all,



I am just returning to my doctoral studies after a 7-month medical leave and 
desperately trying to catch up for lost time. I am COMPLETELY new to 
programming, well, I did try learning C for 3 weeks 3 yrs ago (with very little 
success) but had to stop and
 then spent 2 years in the Amazon climbing trees (lots more enjoyable than 
learning to programme!) and collecting loads of field data that I now need to 
post-process and analyse. By the way, the 3 weeks I spent trying to learn C 
really ended up being spent
 trying to get to grips with using a terminal for the first time in my life. 



Since getting back to work, I was advised to try learning Python instead of C 
as it is a much easier first language to learn. I have been trying, but again, 
to not great success. I started following A Primer on Scientific programming 
with Python but
 I kept getting lost and stuck, specially on the exercises. I have also been 
advised that I should not try to learn programming by following guides but by 
trying to write the programmes I need to analyse my data. Although I can 
understand the logic behind this
 last bit of advise (it gives context and direction to the learning process) I 
have also gotten stuck trying this approach as I do not know how to 
programme!. Thus, I was hoping that some of you can remember how you got 
started and point me towards any really
 good interactive learning guides/materials and/or have a good learning 
strategy for a complete beginner. I have searched the web and was overwhelmed 
by choice of tutorials and guides. I have skimmed through a couple of tutorials 
but then fail to see how all
 that relates to my own work and I get stuck with what seems like basic 
important concepts so I don't progress. I then think I should try to make some 
progress with my own data analysing and go back to trying to learn to write a 
programme for my specific needs
 and get stuck again because this requires more advanced skills then the basic 
programming concepts I have been reading about on the learning guides. So, I am 
now feeling VERY frustrated and have no idea what on Earth I am doing! Can 
anyone please offer guidance
 in my learning process? I don't know how and what I should be spending my time 
learning first and/or if I should focus my learning towards the skill areas I 
will require to write my specific programmes, although I have no idea what 
these are. I would like
 advise on finding some really good interactive(let you know if your solution 
to an exercise is correct or not) and or video tutorials that give you feedback 
on the solutions you write to exercises.   




Many thanks in advance for all your help, it will be much appreciated!








Cecilia Chavana-Bryant

DPhil Candidate - Remote sensing and tropical phenology

Environmental Change Institute

School of Geography and the Environment

University of Oxford

South Parks Road, Oxford, OX1 3QY

Web: http://www.eci.ox.ac.uk/teaching/doctoral/chavanabryantcecilia.php

Tel Direct: +44 (0)1865 275861

Fax: +44 (0)1865 275885









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Re: [Tutor] Hello Python Tutor - help please!

[Steven D'Aprano]

Hello Cecilia,

My replies are below, interleaved with your comments, which are
prefixed with  marks.


On 22/08/12 20:10, Cecilia Chavana-Bryant wrote:


By the way, the 3 weeks I spent trying to learn C really ended up
being spent trying to get to grips with using a terminal for the
first time in my life.


Unfortunately, there will be a certain amount of that, or at least
something quite similar to a terminal. Fortunately, using Python in
the terminal is usually MUCH easier than C, and in my experience
using Python's interactive interpreter is one of the best ways to
learn the language.

What sort of computer are you using? Windows, Linux, Macintosh, or
something different? I think that most of the people here use Linux
or Windows, but we can probably help you one way or the other.



Since getting back to work, I was advised to try learning Python
instead of C as it is a much easier first language to learn.


Yes, definitely, but it is still programming. Don't overestimate
the difficulty, if it was hard programmers couldn't learn to do it
*wink*, but on the other hand it's not trivial either.



I have been trying, but again, to not great success. I started
following A Primer on Scientific programming with Python but I
kept getting lost and stuck, specially on the exercises.


If you are willing to make a good, honest effort on the exercises
first, we're happy to help you with them. We do like to see your
attempt first, so that we can suggest fixes rather than solve the
problem for you.



I have also been advised that I should not try to learn
programming by following guides but by trying to write the
programmes I need to analyse my data. Although I can understand
the logic behind this last bit of advise (it gives context and
direction to the learning process) I have also gotten stuck
trying this approach as I do not know how to programme!.


I'm entirely with you there. Having direction in your learning is
a good thing. But until you understand the basic skills you need,
it will be nothing but frustration and pain!

I recommend that, if nothing else, you work through some basic
tutorials so that you at least have some idea of basic language
constructs like:

- strings
- lists
- functions
- ints
- floats
- basic arithmetic
- importing modules
etc.

You could start with the official Python tutorial:

http://docs.python.org/tutorial/index.html

although I find that it is sometimes a bit wordy. (I should
talk...)

If you get stuck, don't hesitate to come back and ask
questions, that's why we're here.



Thus, I was hoping that some of you can remember how you got
started


I learned from the book Learning Python by Mark Lutz and
David Ascher, and then by writing oodles and oodles of really
bad code which I have long since thrown away :)


[...]

So, I am now feeling VERY frustrated and have no idea what on
Earth I am doing! Can anyone please offer guidance in my
learning process?


I feel your pain! That's how I feel every time I try to understand
monads in Haskell (don't ask!).

How about if you start off with a simple question you would like
to solve using Python? Something relevant to your work. You may
need to explain some of the concepts to us, since we're not
ecologists. (At least, I'm not, I can't speak for others.)

We can then try to guide you to a solution and introduce concepts
as we go.




--
Steven
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Re: [Tutor] Hello Python Tutor - help please!

[Cecilia Chavana-Bryant]

Hola Bill,

Many thanks for your reply to my post, you seem to understand the predicament I 
am in very well. Unfortunately, I am currently working from home and do not 
have someone close by to help and this is why I came to this space. This is 
also why I asked for advise about interactive tutorials or video tutorials. I 
have found that I keep getting lost with the more traditional tutorials where 
you just read and then do exercises. Following the guide I mentioned on my 
initial post I got through the first 2 chapters but I found them quite hard 
going. I don't know if this makes me not a complete beginner but I certainly do 
not feel like I learned much from reading them. Maybe it is the trying to learn 
the computer ecosystem of terminal commands at the same time that is making 
this learning process so tough.

With respect to my field data, during my 2 yrs of fieldwork I collected a large 
amount of data which is currently stored in excel files. My research involves 
remote sensing (data from Earth-observation satellites) and I work with data 
from the MODIS NASA satellite which monitors the health of forest canopies 
using reflectance data. My research is based in the Amazon. I have collected 
field data to monitor the leaf dynamics of canopy leaves during the dry season. 
Dry season is the time of year when many tropical trees change their old leaves 
for new ones. New leaves are more photosynthetically active (absorb more carbon 
from and release more oxygen into the atmosphere) so the leaf exchange of such 
a large forest region as the Amazon can have huge effects on regional and 
global carbon and water cycles and thus on global climate (apologies if I'm 
giving you loads more information than you need or requested?!). My data 
involves a large amount of data on leaf demography (we demographically surveyed 
more than 120,000 leaves), and thousands of morphological and reflectance 
measurements. I will have to reorganise this data and create a few easily 
manipulable datasets so I can sort data according to leaf age, canopy position, 
date, etc. Then I will have to do statistical analyses on the data. I will also 
have to model some of the data.

Many thanks for taking the time to respond to my post so comprehensively and 
for your good wishes.


Cecilia Chavana-Bryant
DPhil Candidate - Remote sensing and tropical phenology
Environmental Change Institute
School of Geography and the Environment
University of Oxford
South Parks Road, Oxford, OX1 3QY
Web: http://www.eci.ox.ac.uk/teaching/doctoral/chavanabryantcecilia.php
Tel Direct: +44 (0)1865 275861
Fax: +44 (0)1865 275885

From: William R. Wing (Bill Wing) [w...@mac.com]
Sent: 22 August 2012 15:17
To: Cecilia Chavana-Bryant
Cc: William R. Wing (Bill Wing)
Subject: Re: [Tutor] Hello Python Tutor - help please!

On Aug 22, 2012, at 6:10 AM, Cecilia Chavana-Bryant 
cecilia.chavana-bry...@ouce.ox.ac.ukmailto:cecilia.chavana-bry...@ouce.ox.ac.uk
 wrote:

Dear all,

I am just returning to my doctoral studies after a 7-month medical leave and 
desperately trying to catch up for lost time. I am COMPLETELY new to 
programming, well, I did try learning C for 3 weeks 3 yrs ago (with very little 
success) but had to stop and then spent 2 years in the Amazon climbing trees 
(lots more enjoyable than learning to programme!) and collecting loads of field 
data that I now need to post-process and analyse. By the way, the 3 weeks I 
spent trying to learn C really ended up being spent trying to get to grips with 
using a terminal for the first time in my life.


Could you say a few words about what the field data is, and how you hope to 
analyze it.  That is, are you headed in the direction of plotting species 
density on maps, or the time evolution of something, or doing statistics?

Since getting back to work, I was advised to try learning Python instead of C 
as it is a much easier first language to learn. I have been trying, but again, 
to not great success. I started following A Primer on Scientific programming 
with Python but I kept getting lost and stuck, specially on the exercises. I 
have also been advised that I should not try to learn programming by following 
guides but by trying to write the programmes I need to analyse my data. 
Although I can understand the logic behind this last bit of advise (it gives 
context and direction to the learning process) I have also gotten stuck trying 
this approach as I do not know how to programme!. Thus, I was hoping that 
some of you can remember how you got started and point me towards any really 
good interactive learning guides/materials and/or have a good learning strategy 
for a complete beginner. I have searched the web and was overwhelmed by choice 
of tutorials and guides. I have skimmed through a couple of tutorials but then 
fail to see how all that relates to my own work and I get stuck with what seems 
like basic important concepts so I don't progress. I then think I

Re: [Tutor] Hello Python Tutor - help please!

[Joel Goldstick]

On Wed, Aug 22, 2012 at 11:33 AM, Cecilia Chavana-Bryant
cecilia.chavana-bry...@ouce.ox.ac.uk wrote:
 Hola Bill,

 Many thanks for your reply to my post, you seem to understand the
 predicament I am in very well. Unfortunately, I am currently working from
 home and do not have someone close by to help and this is why I came to this
 space. This is also why I asked for advise about interactive tutorials or
 video tutorials. I have found that I keep getting lost with the more
 traditional tutorials where you just read and then do exercises. Following
 the guide I mentioned on my initial post I got through the first 2 chapters
 but I found them quite hard going. I don't know if this makes me not a
 complete beginner but I certainly do not feel like I learned much from
 reading them. Maybe it is the trying to learn the computer ecosystem of
 terminal commands at the same time that is making this learning process so
 tough.

 With respect to my field data, during my 2 yrs of fieldwork I collected a
 large amount of data which is currently stored in excel files. My research
 involves remote sensing (data from Earth-observation satellites) and I work
 with data from the MODIS NASA satellite which monitors the health of forest
 canopies using reflectance data. My research is based in the Amazon. I have
 collected field data to monitor the leaf dynamics of canopy leaves during
 the dry season. Dry season is the time of year when many tropical trees
 change their old leaves for new ones. New leaves are more photosynthetically
 active (absorb more carbon from and release more oxygen into the atmosphere)
 so the leaf exchange of such a large forest region as the Amazon can have
 huge effects on regional and global carbon and water cycles and thus on
 global climate (apologies if I'm giving you loads more information than you
 need or requested?!). My data involves a large amount of data on leaf
 demography (we demographically surveyed more than 120,000 leaves), and
 thousands of morphological and reflectance measurements. I will have to
 reorganise this data and create a few easily manipulable datasets so I can
 sort data according to leaf age, canopy position, date, etc. Then I will
 have to do statistical analyses on the data. I will also have to model some
 of the data.

 Many thanks for taking the time to respond to my post so comprehensively and
 for your good wishes.


 Cecilia Chavana-Bryant
 DPhil Candidate - Remote sensing and tropical phenology
 Environmental Change Institute
 School of Geography and the Environment
 University of Oxford
 South Parks Road, Oxford, OX1 3QY
 Web: http://www.eci.ox.ac.uk/teaching/doctoral/chavanabryantcecilia.php
 Tel Direct: +44 (0)1865 275861
 Fax: +44 (0)1865 275885
 
 From: William R. Wing (Bill Wing) [w...@mac.com]
 Sent: 22 August 2012 15:17
 To: Cecilia Chavana-Bryant
 Cc: William R. Wing (Bill Wing)
 Subject: Re: [Tutor] Hello Python Tutor - help please!

 On Aug 22, 2012, at 6:10 AM, Cecilia Chavana-Bryant
 cecilia.chavana-bry...@ouce.ox.ac.uk wrote:

 Dear all,

 I am just returning to my doctoral studies after a 7-month medical leave and
 desperately trying to catch up for lost time. I am COMPLETELY new to
 programming, well, I did try learning C for 3 weeks 3 yrs ago (with very
 little success) but had to stop and then spent 2 years in the Amazon
 climbing trees (lots more enjoyable than learning to programme!) and
 collecting loads of field data that I now need to post-process and analyse.
 By the way, the 3 weeks I spent trying to learn C really ended up being
 spent trying to get to grips with using a terminal for the first time in my
 life.


 Could you say a few words about what the field data is, and how you hope to
 analyze it.  That is, are you headed in the direction of plotting species
 density on maps, or the time evolution of something, or doing statistics?

 Since getting back to work, I was advised to try learning Python instead of
 C as it is a much easier first language to learn. I have been trying, but
 again, to not great success. I started following A Primer on Scientific
 programming with Python but I kept getting lost and stuck, specially on the
 exercises. I have also been advised that I should not try to learn
 programming by following guides but by trying to write the programmes I need
 to analyse my data. Although I can understand the logic behind this last bit
 of advise (it gives context and direction to the learning process) I have
 also gotten stuck trying this approach as I do not know how to programme!.
 Thus, I was hoping that some of you can remember how you got started and
 point me towards any really good interactive learning guides/materials
 and/or have a good learning strategy for a complete beginner. I have
 searched the web and was overwhelmed by choice of tutorials and guides. I
 have skimmed through a couple of tutorials but then fail to see how all that
 relates to my own work and I get

Re: [Tutor] Hello Python Tutor - help please!

[Alan Gauld]

On 22/08/12 11:10, Cecilia Chavana-Bryant wrote:


I do not know how to programme!. Thus, I was hoping that some of you
can remember how you got started and point me towards any really good
interactive learning guides/materials and/or have a good learning
strategy for a complete beginner.


At the risk of self promotion you could try the early stages of my 
tutorial (see .sig).


It starts from level zero and explains the concepts of programming 
before getting started writing code. I personally found that to be 
fundamental to my learning when I started (and why I included it!).


It then goes through the basic programming structures using very
simple examples - a multiplication table and address book mainly.
(It includes VBScript and Javascript examples too but feel free to 
ignore them if you find they confuse more than help! The intent is to 
show the common structures present in all programming languages :-)


Whether you progress beyond the first two sections depends on what you 
want to do next. Those would be enough to start writing programs related 
to your work and switching to another tutor at that point

might be effective.

But the concepts topics at the start of my tutor are I think
relatively unique, and if diving straight into writing code isn't 
working maybe a view of the bigger picture will help.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] Hello Python Tutor - help please!

[Walter Prins]

Hi Cecilia,

You've had a lot of good replies already, but I'd like to add the
following points if I may:

1) You probably should figure out as much as that's possible up front
exactly you're trying to do in terms of data processing first (e.g.
some idea of the stats, graphs, summaries, operations etc), and then
figure out whether Python is in fact the quickest/best way to get
there for you.  Python is very capable, it has many data analysis
libraries and so on and is used by many scientists (NumPy, SciPy,
Pandas comes to mind offhand), but then there are also many other
languages and system also appropriate in this sphere.  (R comes to
mind.)  Your goal (from my point of view) is not to become a
programmer, but to get your research done.  Python may be the way to
achieve that, but from where I'm sitting it may also not be.

2) It may be useful to take some suitable courses from some of the
very good free online courses now available from various sources such
as Coursera.  Some examples that seem relevant:

Computing for Data Analysis:
https://www.coursera.org/course/compdata

Mathematics Biostatistics Boot camp:
https://www.coursera.org/course/biostats

Data Analysis
https://www.coursera.org/course/dataanalysis

There are also courses covering basic programming, including Python,
for example: https://www.coursera.org/course/programming1

HTH,

Walter
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Re: [Tutor] Hello Python Tutor - help please!

[Ray Jones]

I highly recommend the Google Python class that is found on YouTube.
The first video is found at http://www.youtube.com/watch?v=tKTZoB2Vjuk
The supporting class materials and assignments are found at
http://code.google.com/edu/languages/google-python-class/ . This series
of videos begins at a pretty basic level, but subsequent videos increase
the difficulty level pretty rapidly.

Don't despair - the concept of how to properly manipulate strings,
lists, tuples, and other objects is rather daunting, but if you're
working on your doctoral studies, you already know that complex concepts
aren't simply soaked up like water to a sponge ;).


Ray

On 08/22/2012 03:10 AM, Cecilia Chavana-Bryant wrote:
 Dear all,

 I am just returning to my doctoral studies after a 7-month medical
 leave and desperately trying to catch up for lost time. I am
 COMPLETELY new to programming, well, I did try learning C for 3 weeks
 3 yrs ago (with very little success) but had to stop and then spent 2
 years in the Amazon climbing trees (lots more enjoyable than learning
 to programme!) and collecting loads of field data that I now need to
 post-process and analyse. By the way, the 3 weeks I spent trying to
 learn C really ended up being spent trying to get to grips with using
 a terminal for the first time in my life. 

 Since getting back to work, I was advised to try learning Python
 instead of C as it is a much easier first language to learn. I have
 been trying, but again, to not great success. I started following A
 Primer on Scientific programming with Python but I kept getting lost
 and stuck, specially on the exercises. I have also been advised that I
 should not try to learn programming by following guides but by trying
 to write the programmes I need to analyse my data. Although I can
 understand the logic behind this last bit of advise (it gives context
 and direction to the learning process) I have also gotten stuck trying
 this approach as I do not know how to programme!. Thus, I was hoping
 that some of you can remember how you got started and point me towards
 any really good interactive learning guides/materials and/or have a
 good learning strategy for a complete beginner. I have searched the
 web and was overwhelmed by choice of tutorials and guides. I have
 skimmed through a couple of tutorials but then fail to see how all
 that relates to my own work and I get stuck with what seems like basic
 important concepts so I don't progress. I then think I should try to
 make some progress with my own data analysing and go back to trying to
 learn to write a programme for my specific needs and get stuck again
 because this requires more advanced skills then the basic programming
 concepts I have been reading about on the learning guides. So, I am
 now feeling VERY frustrated and have no idea what on Earth I am doing!
 Can anyone please offer guidance in my learning process? I don't know
 how and what I should be spending my time learning first and/or if I
 should focus my learning towards the skill areas I will require to
 write my specific programmes, although I have no idea what these are.
 I would like advise on finding some really good interactive(let you
 know if your solution to an exercise is correct or not) and or video
 tutorials that give you feedback on the solutions you write to
 exercises.   

 Many thanks in advance for all your help, it will be much appreciated!
 


 Cecilia Chavana-Bryant
 DPhil Candidate - Remote sensing and tropical phenology
 Environmental Change Institute
 School of Geography and the Environment
 University of Oxford
 South Parks Road, Oxford, OX1 3QY
 Web: http://www.eci.ox.ac.uk/teaching/doctoral/chavanabryantcecilia.php
 Tel Direct: +44 (0)1865 275861
 Fax: +44 (0)1865 275885


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[Tutor] Hello Python Tutor - help please!

[Cecilia Chavana-Bryant]

Steven, (now from my new account without all the long-winded signature) can
files be attached to posts in this forum?

Cecilia
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Re: [Tutor] Hello Python Tutor - help please!

[Alan Gauld]

On 22/08/12 22:51, Cecilia Chavana-Bryant wrote:

Steven, (now from my new account without all the long-winded signature)
can files be attached to posts in this forum?


Yes they can, but we prefer if you just include them in the body if they 
are fairly short (100 lines?) or put them on a pastebin with a link.


Some mail tools/servers/smartphones don't like mail attachments.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] Hello Python Tutor - help please!

[Alan Gauld]

On 22/08/12 21:51, Cecilia Chavana-Bryant wrote:


def main(fname, sheet_name):
 wb = xlrd.open_workbook(fname)
 sh = wb.sheet_by_name(sheet_name)
 data1 = sh.col_values(0)
 data2 = sh.col_values(1)

 return data1, data2

fname = Cal_File_P17.xlsx
sheet_name = RefPanelData
(data1, data2) = main(fname)

print data1, data2

... I do not know where the data is being saved to.



That's because it isn't being saved anywhere, it gets
thrown away after printing it.

If you want to save it you need to augment/replace the print
statement with a file write statement(s)

You could also write it out using the OS redirection facility.
On Unix (ie Your MacOS Terminal) thats done by running the
program like:

$ python myprog.py  myOutputFile.txt

Where you substitute your own desired program name and
output filename of course!

But that will just create a text file that looks like the output 
displayed on the Terminal, which is not, I think, what you are after.

You probably want to do some extra work to save as a csv file.

However, before you do that you could look at using the spreadsheet's 
SaveAs feature to export as a CSV directly, but it depends on how many 
spreadsheets you need to convert!


HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] hello~

[Prasad, Ramit]

as you can see i only use some of the command. it doesnt produce an error 
message tho.. just repeats return Error(b%s/b I couldn't find %s 
anywhere, user.name.title(), name.title())

Your problem might be is indenting of the else. It is indenting 
to be a for...else loop. Which means that if nothing breaks out of the
loop it will always do what is in the else (which in this case returns
Error[...]) after the loop has finished running through the rooms.

        for room in mgr.rooms:
                if data[1] == join:
                        mgr.sendObject(target, Html(b%s/b, bfont 
color='#3399CC'%s/font/b wants to tell you bi%s/i/b, name.title, 
user.name.title$
        else:
                        return Error(b%s/b I couldn't find %s anywhere, 
user.name.title(), name.title())


Why are you looping through the rooms and checking if data[1] == join?
You do not even use the room object in the loop, and target is not defined
in the local scope, although I suppose you meant to use room instead.
This loop just smells to me. 

Ramit


Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology
712 Main Street | Houston, TX 77002
work phone: 713 - 216 - 5423

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available at http://www.jpmorgan.com/pages/disclosures/email.  
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Re: [Tutor] hello~

[Keitaro Kaoru]

i resent it but if that doesnt work. cause i sent it to myself also
looks fine on my gmail.. but heres a link to pastebin

http://pastebin.com/Jp7VJKGB
 maybe thatll help?
On Mon, May 14, 2012 at 1:43 AM, Russel Winder rus...@winder.org.uk wrote:
 On Mon, 2012-05-14 at 00:19 +0100, Mark Lawrence wrote:
 [...]
 Sorry but it's unreadable to me.  Have you sent this in HTML when you
 should have sent in plain text?

 I think it is just line wrapping, email still is supposed to have no
 lines greater that 78 characters (RFC 2822) and some email clients
 enforce this on sending by amending what the author thought they sent.

 --
 Russel.
 =
 Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.win...@ekiga.net
 41 Buckmaster Road    m: +44 7770 465 077   xmpp: rus...@winder.org.uk
 London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder

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-- 
~~Austin
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[Tutor] hello~

[Keitaro Kaoru]

hey. Austin here for some reason this command. all it does it produces the
error message at the bottom.. itll say my name and the persons name im
trying to send the message to but thats it. heres the command.

mgr.addCommand(tell, 1, send a person a message to the rooms he is in,
tell, unlisted = True)

def tell(mgr, croom, user, msg, args):
name = args.lower().split( )[0]
if not name.isalnum(): return Html(Non-alphanumeric name,
seriously?)
data = shared_db.get(seen: + name)
if data == None:
return Html(I have no records about this user.)
data = json.loads(data)
for room in mgr.rooms:
if data[1] == join:
mgr.sendObject(target, Html(b%s/b, bfont
color='#3399CC'%s/font/b wants to tell you bi%s/i/b,
name.title, user.name.title$
else:
return Error(b%s/b I couldn't find %s
anywhere, user.name.title(), name.title())

i built it off these 2 commands

def broadcast(mgr, croom, user, msg, args):
for room in mgr.rooms:
mgr.sendObject(room, Html(Broadcast by b%s/b:%s,
user.name, args))

def seen(mgr, room, user, msg, args):
name = args.lower().split( )[0]
if not name.isalnum(): return Html(Non-alphanumeric name, seriously?)
data = shared_db.get(seen: + name)
if data == None:
return Html(I have no records about this user.)
data = json.loads(data)
ifdata[1] == join:
return Html(Last seen b%s/b join b%s/b, b%s/b ago., name,
data[0], tdelta(data[2]))
elif data[1] == leave:
return Html(Last seen b%s/b leave b%s/b, b%s/b ago., name,
data[0], tdelta(data[2]))
elif data[1] == message:
return Html(Last seen b%s/b message in b%s/b, b%s/b ago:
i\%s\/i, name, data[0], tdelta(data[2]), data[3])
return Html(I have no records about this user.)

as you can see i only use some of the command. it doesnt produce an error
message tho.. just repeats return Error(b%s/b I couldn't find %s
anywhere, user.name.title(), name.title())
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Re: [Tutor] hello~

[Mark Lawrence]

On 14/05/2012 00:04, Keitaro Kaoru wrote:

hey. Austin here for some reason this command. all it does it produces the
error message at the bottom.. itll say my name and the persons name im
trying to send the message to but thats it. heres the command.

mgr.addCommand(tell, 1, send a person a message to the rooms he is in,
tell, unlisted = True)

def tell(mgr, croom, user, msg, args):
 name = args.lower().split( )[0]
 if not name.isalnum(): return Html(Non-alphanumeric name,
seriously?)
 data = shared_db.get(seen: + name)
 if data == None:
 return Html(I have no records about this user.)
 data = json.loads(data)
 for room in mgr.rooms:
 if data[1] == join:
 mgr.sendObject(target, Html(b%s/b,bfont
color='#3399CC'%s/font/b  wants to tell youbi%s/i/b,
name.title, user.name.title$
 else:
 return Error(b%s/b  I couldn't find %s
anywhere, user.name.title(), name.title())

i built it off these 2 commands

def broadcast(mgr, croom, user, msg, args):
 for room in mgr.rooms:
 mgr.sendObject(room, Html(Broadcast byb%s/b:%s,
user.name, args))

def seen(mgr, room, user, msg, args):
name = args.lower().split( )[0]
if not name.isalnum(): return Html(Non-alphanumeric name, seriously?)
data = shared_db.get(seen: + name)
if data == None:
return Html(I have no records about this user.)
data = json.loads(data)
ifdata[1] == join:
return Html(Last seenb%s/b  joinb%s/b,b%s/b  ago., name,
data[0], tdelta(data[2]))
elif data[1] == leave:
return Html(Last seenb%s/b  leaveb%s/b,b%s/b  ago., name,
data[0], tdelta(data[2]))
elif data[1] == message:
return Html(Last seenb%s/b  message inb%s/b,b%s/b  ago:
i\%s\/i, name, data[0], tdelta(data[2]), data[3])
return Html(I have no records about this user.)

as you can see i only use some of the command. it doesnt produce an error
message tho.. just repeats return Error(b%s/b  I couldn't find %s
anywhere, user.name.title(), name.title())




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Sorry but it's unreadable to me.  Have you sent this in HTML when you 
should have sent in plain text?


--
Cheers.

Mark Lawrence.

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Re: [Tutor] hello~

[Russel Winder]

On Mon, 2012-05-14 at 00:19 +0100, Mark Lawrence wrote:
[...]
 Sorry but it's unreadable to me.  Have you sent this in HTML when you 
 should have sent in plain text?

I think it is just line wrapping, email still is supposed to have no
lines greater that 78 characters (RFC 2822) and some email clients
enforce this on sending by amending what the author thought they sent.

-- 
Russel.
=
Dr Russel Winder  t: +44 20 7585 2200   voip: sip:russel.win...@ekiga.net
41 Buckmaster Roadm: +44 7770 465 077   xmpp: rus...@winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder


signature.asc
Description: This is a digitally signed message part
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Re: [Tutor] Hello again. Still the same problem, different question.

[Robert Sjoblom]

On 12 November 2011 07:27,  tutor-requ...@python.org wrote:
 Send Tutor mailing list submissions to
        tutor@python.org

 To subscribe or unsubscribe via the World Wide Web, visit
        http://mail.python.org/mailman/listinfo/tutor
 or, via email, send a message with subject or body 'help' to
        tutor-requ...@python.org

 You can reach the person managing the list at
Please have a useful subject line next time, the current subject
doesn't tell us anything about your problem.

 Someone there told me they would've given up by now but I am not giving up
 on this one or anything else. Just to give you a heads up, you will be
 getting questions about this until this program works.

You can't force me to answer questions! Additionally; I, for one, will
put you on ignore if you spam this list with questions that are about
the same subject and are unsolvable because the standard version
doesn't work. So just to give you a heads up: don't overextend your
welcome.

-- 
best regards,
Robert S.
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[Tutor] Hello again. Still the same problem, different question.

[Nathaniel Trujillo]

I realize that one of you told me that there is no livewires for python
v3.1.1 but the book that I am reading teaches v3.1.1 and the code that is
presented in the book has a line that imports a module from the livewires
package. Now since the book covers v3.1.1, I would have to conclude that
the code containing the line from livewires import games should work in
version 3.1.1. They gave me a website to go and download a version of
livewires that would work (www.courseptr.com/downloads) and I went there
but I could not find that download anywhere. I think the website might have
changed since the book was written. If anybody knows where I can get the
version of livewires I need I would be truly greatful. My book is entitled
Python Programming for the Absolute Beginner Third Edition. Anyway, here is
the code that my book insists should work.

# New Graphics Window
# Demonstrates creating a graphics window
from livewires import games
games.init(screen_width = 640, screen_height = 480, fps = 50)
games.screen.mainloop()
and here is the error message I keep getting

Traceback (most recent call last):
  File C:\Python27\new_graphics_window.py, line 6, in module
games.init(screen_width = 640, screen_height = 480, fps = 50)
AttributeError: 'module' object has no attribute 'init'

Someone there told me they would've given up by now but I am not giving up
on this one or anything else. Just to give you a heads up, you will be
getting questions about this until this program works. Thanks for your help.
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Re: [Tutor] Hello again. Still the same problem, different question.

[delegbede]

Can you kindly mail the author?
That might be a better way to have this resolved. 
Its interesting you are sticking with python v3. 
Cheers. 
Sent from my BlackBerry wireless device from MTN

-Original Message-
From: Nathaniel Trujillo hothottr...@gmail.com
Sender: tutor-bounces+delegbede=dudupay@python.org
Date: Fri, 11 Nov 2011 21:16:30 
To: Tutor@python.org
Subject: [Tutor] Hello again. Still the same problem, different question.

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Re: [Tutor] Hello again. Still the same problem, different question.

[Steven D'Aprano]

Nathaniel Trujillo wrote:

I realize that one of you told me that there is no livewires for python
v3.1.1 but the book that I am reading teaches v3.1.1 and the code that is
presented in the book has a line that imports a module from the livewires
package. Now since the book covers v3.1.1, I would have to conclude that
the code containing the line from livewires import games should work in
version 3.1.1. They gave me a website to go and download a version of
livewires that would work (www.courseptr.com/downloads) and I went there
but I could not find that download anywhere. I think the website might have
changed since the book was written. If anybody knows where I can get the
version of livewires I need I would be truly greatful. My book is entitled
Python Programming for the Absolute Beginner Third Edition. Anyway, here is
the code that my book insists should work.


According to one of the reviews on Amazon, that's because the author of 
the book has written his own customized version of Livewires which you 
have to use.


http://www.amazon.ca/Python-Programming-Absolute-Beginner-Second/dp/1598631128

The book quite clearly says so too:

TRAP Although you're welcome to visit the web site of the LiveWires
 organization at http://www.livewires.org.uk , be aware that the 


 livewires package used in this book is a modified version of the
 package that LiveWires created.




Someone there told me they would've given up by now but I am not giving up
on this one or anything else. Just to give you a heads up, you will be
getting questions about this until this program works. Thanks for your help.


While I admire your persistence, we are all volunteers and may not 
appreciate being asked the same questions over and over and over again 
to no value.


I'm just saying that at some point, you may have to expect that we'll 
stop answering questions if we think we're just wasting our time. If the 
author's custom version is not available, and the standard version 
doesn't work, then we're probably wasting our time.




--
Steven
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Re: [Tutor] Hello again. Still the same problem, different question.

[Andreas Perstinger]

On 2011-11-12 05:16, Nathaniel Trujillo wrote:

They gave me a website to go and download a version of
livewires that would work (www.courseptr.com/downloads) and I went there
but I could not find that download anywhere.


http://www.delmarlearning.com/companions/content/1435455002/downloads/index.asp?isbn=1435455002
If you click on Book related software you'll get a zip-file which 
includes livewires.


Bye, Andreas
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Re: [Tutor] Hello World in Python without space

[Lisi]

On Saturday 16 July 2011 03:15:12 Richard D. Moores wrote:
 But that makes me wonder if there isn't a simpler way to do it with
 Python -- to delete the contents of a file without deleting the file?

Up to now, knowing no better ;-), I have opened the file in, or copied and 
pasted the contents of a file into, a word processor and turned on the 
non-printing characters.  It is then easy to see extraneous spaces, empty 
lines etc.  I then go back to the editor and do the revealed editing.

Rough, ready and cobbled - but easy, and it works. ;-)

If you use Windows and have no idea what I am talking about, I apologise.  It 
is so long since I used Windows that I have forgotten much of what it can and 
cannot do; and I don't know whether it can do this.

Lisi
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Re: [Tutor] Hello World in Python without space

[Richard D. Moores]

On Sun, Jul 10, 2011 at 05:05, Peter Otten __pete...@web.de wrote:

  help(print)

 shows

 print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout)

    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file: a file-like object (stream); defaults to the current sys.stdout.
    sep:  string inserted between values, default a space.
    end:  string appended after the last value, default a newline.

I didn't know that printing to a file with print() was possible, so I tried

 print(Hello, world!, file=C:\test\test.txt)
Traceback (most recent call last):
  File string, line 1, in fragment
builtins.AttributeError: 'str' object has no attribute 'write'


And the docs at
http://docs.python.org/py3k/library/functions.html#print tell me
The file argument must be an object with a write(string) method; if
it is not present or None, sys.stdout will be used.

What do I do to test.txt to make it an object with a write(string) method?

Thanks,

Dick Moores
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Re: [Tutor] Hello World in Python without space

[Stefan Behnel]

Richard D. Moores, 15.07.2011 23:21:

On Sun, Jul 10, 2011 at 05:05, Peter Otten wrote:


 help(print)

shows

print(...)
print(value, ..., sep=' ', end='\n', file=sys.stdout)

Prints the values to a stream, or to sys.stdout by default.
Optional keyword arguments:
file: a file-like object (stream); defaults to the current sys.stdout.
sep:  string inserted between values, default a space.
end:  string appended after the last value, default a newline.


I didn't know that printing to a file with print() was possible, so I tried

 print(Hello, world!, file=C:\test\test.txt)
Traceback (most recent call last):
   File string, line 1, infragment
builtins.AttributeError: 'str' object has no attribute 'write'


And the docs at
http://docs.python.org/py3k/library/functions.html#print  tell me
The file argument must be an object with a write(string) method; if
it is not present or None, sys.stdout will be used.

What do I do to test.txt to make it an object with a write(string) method?


Oh, there are countless ways to do that, e.g.

  class Writable(object):
  def __init__(self, something):
  print(Found a %s % something))
  def write(self, s):
  print(s)

  print(Hello, world!, file=Writable(C:\\test\\test.txt))

However, I'm fairly sure what you want is this:

with open(C:\\test\\test.txt, w) as file_object:
print(Hello, world!, file=file_object)

Look up open() (open a file) and the with statement (used here 
basically as a safe way to make sure the file is closed after writing).


Also note that \t refers to a TAB character in Python, you used this 
twice in your file path string.


Stefan

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Re: [Tutor] Hello World in Python without space

[Richard D. Moores]

On Fri, Jul 15, 2011 at 14:47, Stefan Behnel stefan...@behnel.de wrote:
 Richard D. Moores, 15.07.2011 23:21:

 What do I do to test.txt to make it an object with a write(string)
 method?

 Oh, there are countless ways to do that, e.g.

  class Writable(object):
      def __init__(self, something):
          print(Found a %s % something))
      def write(self, s):
          print(s)

  print(Hello, world!, file=Writable(C:\\test\\test.txt))

 However, I'm fairly sure what you want is this:

    with open(C:\\test\\test.txt, w) as file_object:
        print(Hello, world!, file=file_object)

Yes, went with

with open(C:\\test\\test.txt, a+) as file_object:
  print(Hello, world!, file=file_object)

 Look up open() (open a file) and the with statement (used here basically
 as a safe way to make sure the file is closed after writing).

 Also note that \t refers to a TAB character in Python, you used this twice
 in your file path string.

Oops. I'd forgotten about that.

Thanks very much, Stefan and Donald.

Dick
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Re: [Tutor] Hello World in Python without space

[xDog Walker]

On Friday 2011 July 15 15:58, Richard D. Moores wrote:
 On Fri, Jul 15, 2011 at 14:47, Stefan Behnel stefan...@behnel.de wrote:
  Richard D. Moores, 15.07.2011 23:21:
  What do I do to test.txt to make it an object with a write(string)
  method?
 
  Oh, there are countless ways to do that, e.g.
 
   class Writable(object):
       def __init__(self, something):
           print(Found a %s % something))
       def write(self, s):
           print(s)
 
   print(Hello, world!, file=Writable(C:\\test\\test.txt))
 
  However, I'm fairly sure what you want is this:
 
     with open(C:\\test\\test.txt, w) as file_object:
         print(Hello, world!, file=file_object)

 Yes, went with

 with open(C:\\test\\test.txt, a+) as file_object:
   print(Hello, world!, file=file_object)

  Look up open() (open a file) and the with statement (used here
  basically as a safe way to make sure the file is closed after writing).
 
  Also note that \t refers to a TAB character in Python, you used this
  twice in your file path string.

I believe on Windows, you can almost always use a forward slash in a path: 
C:/somewhere/somewhereelse/

-- 
I have seen the future and I am not in it.
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Re: [Tutor] Hello World in Python without space

[Richard D. Moores]

On Fri, Jul 15, 2011 at 16:21, xDog Walker thud...@gmail.com wrote:

 I believe on Windows, you can almost always use a forward slash in a path:
 C:/somewhere/somewhereelse/

with open(C:/test/test.txt, a) as file_object:
 print(Hello, world!, file=file_object)

Yes, that works for me with Windows Vista. However, if test.txt is
empty, it puts in a blank line as line 1; line 2 is Hello, world!.

Dick
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Re: [Tutor] Hello World in Python without space

[Dave Angel]

On 07/15/2011 07:39 PM, Richard D. Moores wrote:

On Fri, Jul 15, 2011 at 16:21, xDog Walkerthud...@gmail.com  wrote:


I believe on Windows, you can almost always use a forward slash in a path:
C:/somewhere/somewhereelse/

with open(C:/test/test.txt, a) as file_object:
  print(Hello, world!, file=file_object)

Yes, that works for me with Windows Vista. However, if test.txt is
empty, it puts in a blank line as line 1; line 2 is Hello, world!.

Dick
_
I expect that your extra newline was already in the empty file.  It 
cannot have anything to do with using the forward slash for the filename.


DaveA



--

DaveA

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Re: [Tutor] Hello World in Python without space

[Richard D. Moores]

On Fri, Jul 15, 2011 at 17:16, Dave Angel d...@davea.name wrote:
 On 07/15/2011 07:39 PM, Richard D. Moores wrote:

 with open(C:/test/test.txt, a) as file_object:
      print(Hello, world!, file=file_object)

 Yes, that works for me with Windows Vista. However, if test.txt is
 empty, it puts in a blank line as line 1; line 2 is Hello, world!.

 Dick
 _

 I expect that your extra newline was already in the empty file.  It cannot
 have anything to do with using the forward slash for the filename.

I see that you are correct. It seems that selecting all the text in a
text file (in Notepad), then hitting the delete key doesn't guarantee
that the file will be left truly blank. The way that consistently
works for me is to place the cursor in the upper left corner of the
file and hold down the delete key.

Running

with open(C:/test/test.txt, w) as file_object:
  print(file=file_object)

Also works.

But that makes me wonder if there isn't a simpler way to do it with
Python -- to delete the contents of a file without deleting the file?

Dick
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Re: [Tutor] Hello World in Python without space

[Steven D'Aprano]

Richard D. Moores wrote:


But that makes me wonder if there isn't a simpler way to do it with
Python -- to delete the contents of a file without deleting the file?


Opening a file for writing will flush the contents.

open(filename, 'w')

will do it, taking advantage of Python's garbage collector to 
(eventually) close the file. The more careful way is hardly any harder:


open(filename, 'w').close()

and this ensures that the file isn't left open any longer than necessary.


--
Steven
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Re: [Tutor] Hello World in Python without space

[Richard D. Moores]

On Fri, Jul 15, 2011 at 21:38, Steven D'Aprano st...@pearwood.info wrote:

 Richard D. Moores wrote:

 But that makes me wonder if there isn't a simpler way to do it with
 Python -- to delete the contents of a file without deleting the file?

 Opening a file for writing will flush the contents.

 open(filename, 'w')

 will do it, taking advantage of Python's garbage collector to (eventually) 
 close the file. The more careful way is hardly any harder:

 open(filename, 'w').close()

 and this ensures that the file isn't left open any longer than necessary.

open(C:/test/test.txt, 'w').close()

Good to know. Thanks, Steven.

Dick
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Re: [Tutor] Hello World in Python without space

[Emile van Sebille]

On 7/10/2011 4:12 AM Robert H said...

Dear all,


I have Python 3.2 installed on Windows 7. I am a complete beginner
playing around with the basic functions. My problem is the following script:


name=world
print(Hello, name,!)


print(Hello, name+!)

Alan mentioned using concatenation as well and .join() is generally 
preferred, particularly when many strings are involved.


Emile


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[Tutor] Hello World in Python without space

[Robert H]

Dear all,


I have Python 3.2 installed on Windows 7. I am a complete beginner playing 
around with the basic functions. My problem is the following script:


name=world
print(Hello, name,!)


The result is:
Hello world !


However, I don't want the space before the exclamation mark. I want this:
Hello world!


I tried to solve the problem with e.g.:
print(Hello,name.strip(),!)
but the result is the same.


Can anyone out there help me? Thank you.


Regards,
Robert
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Re: [Tutor] Hello World in Python without space

[Izz ad-Din Ruhulessin]

Sending args to the print command always puts spaces between them.

Try:
print(Hello {name}!.format(name=name))





2011/7/10 Robert H hrober...@hotmail.com

  Dear all,


 I have Python 3.2 installed on Windows 7. I am a complete beginner playing
 around with the basic functions. My problem is the following script:


 name=world
 print(Hello, name,!)


 The result is:
 Hello world !


 However, I don't want the space before the exclamation mark. I want this:
 Hello world!


 I tried to solve the problem with e.g.:
 print(Hello,name.strip(),!)
 but the result is the same.


 Can anyone out there help me? Thank you.


 Regards,
 Robert

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Re: [Tutor] Hello World in Python without space

[Peter Otten]

Robert H wrote:

 I have Python 3.2 installed on Windows 7. I am a complete beginner playing
 around with the basic functions. My problem is the following script:
 
 
 name=world
 print(Hello, name,!)
 
 
 The result is:
 Hello world !
 
 
 However, I don't want the space before the exclamation mark. I want this:
 Hello world!
 
 
 I tried to solve the problem with e.g.:
 print(Hello,name.strip(),!)
 but the result is the same.


print() by default inserts a space between its arguments. You can avoid that 
by specifying a separator explicitly with the sep keyword. Let me show it 
in the interactive interpreter which is generally a good place to experiment 
with small snippets of code:

 name = Robert
 print(Hello , name, !, sep=) # Note the explicit   after Hello
Hello Robert!

Another goodie is that you can easily get useful information about modules, 
classes, keywords, and functions, e. g.

 help(print)

shows

print(...)
print(value, ..., sep=' ', end='\n', file=sys.stdout)

Prints the values to a stream, or to sys.stdout by default.
Optional keyword arguments:
file: a file-like object (stream); defaults to the current sys.stdout.
sep:  string inserted between values, default a space.
end:  string appended after the last value, default a newline.

Use help() without argument to learn more about the interactive help.


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Re: [Tutor] Hello World in Python without space

[Alan Gauld]

Robert H hrober...@hotmail.com wrote


name=world
print(Hello, name,!)
Hello world !

However, I don't want the space before the exclamation
mark. I want this:
Hello world!



Can anyone out there help me? Thank you.


I see you've already had two answers, a third is
to construct the string before printing it. There
are various ways to do that:

The simplest:

output = Hello  + name + !

An alternative which is more efficient for
larger numbers of substruings is:

output = .join([Hello ,name,!])  # thats an empty string to 
start


The thirs is to use a formatstring, but thats
what Izz did in his print call.

Whichever method you use you then use

print(output)

Lots of options. As Peter said, use the  prompt to
experiment to find which works best for you.


--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/





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[Tutor] Hello

[Samuel de Champlain]

This is my first message to this mailing list.
I want to create a project with glade and pygtk on fedora.
Can you suggest a good IDE?
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Re: [Tutor] Hello

[Shashwat Anand]

The choice of IDE is quite objective. Many of the people use vim/emacs
exclusively for all the work. Eclipse with PyDev plugin too is a good
choice.

On Thu, Jan 21, 2010 at 11:03 PM, Samuel de Champlain 
samueldechampl...@gmail.com wrote:

 This is my first message to this mailing list.
 I want to create a project with glade and pygtk on fedora.
 Can you suggest a good IDE?

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Re: [Tutor] Hello

[Robert]

Check out wingware IDE and Geany.


On Thu, Jan 21, 2010 at 12:33 PM, Samuel de Champlain
samueldechampl...@gmail.com wrote:
 This is my first message to this mailing list.
 I want to create a project with glade and pygtk on fedora.
 Can you suggest a good IDE?

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Re: [Tutor] Hello

[vishwajeet singh]

 On Thu, Jan 21, 2010 at 11:03 PM, Samuel de Champlain 
 samueldechampl...@gmail.com wrote:

 This is my first message to this mailing list.
 I want to create a project with glade and pygtk on fedora.
 Can you suggest a good IDE?



   netbeans have worked quite well for me but its heavy weight if you are
looking for something light check out komodo.



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-- 
Vishwajeet Singh
+91-9657702154 | dextrou...@gmail.com | http://singhvishwajeet.com
Twitter: http://twitter.com/vishwajeets | LinkedIn:
http://www.linkedin.com/in/singhvishwajeet
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[Tutor] 'Hello world'

[Eldon L Mello Jr]

Hi there,

I must say I'm quite embarrassed about my issue. Ok, I'm a 101% newbie in 
programming and all but I honestly didn't expect I would have problems in my 
very first step which was just to print 'hello world'.


Despite some idiot little thing I might be overlooking I wonder if Python 
3.1.1 was properly installed in my machine. I got a AMD Turion X2 64 
processor and Win7 Pro-64 so I suppose the Python 3.1.1 AMD64 version I got 
was the best pick right?


here it comes:

Python 3.1.1 (r311:74483, Aug 17 2009, 16:45:59) [MSC v.1500 64 bit (AMD64)] 
on win32

Type copyright, credits or license() for more information.

print 'hello world!'

SyntaxError: invalid syntax (pyshell#0, line 1)

print hello world!

SyntaxError: invalid syntax (pyshell#1, line 1)




Thanks a million,

 Eldon. 


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Re: [Tutor] 'Hello world'

[Andre Engels]

On Fri, Jan 1, 2010 at 11:17 AM, Eldon L Mello Jr eldo...@hotmail.com wrote:
 Hi there,

 I must say I'm quite embarrassed about my issue. Ok, I'm a 101% newbie in
 programming and all but I honestly didn't expect I would have problems in my
 very first step which was just to print 'hello world'.

 Despite some idiot little thing I might be overlooking I wonder if Python
 3.1.1 was properly installed in my machine. I got a AMD Turion X2 64
 processor and Win7 Pro-64 so I suppose the Python 3.1.1 AMD64 version I got
 was the best pick right?

 here it comes:

 Python 3.1.1 (r311:74483, Aug 17 2009, 16:45:59) [MSC v.1500 64 bit (AMD64)]
 on win32
 Type copyright, credits or license() for more information.

 print 'hello world!'

 SyntaxError: invalid syntax (pyshell#0, line 1)

 print hello world!

 SyntaxError: invalid syntax (pyshell#1, line 1)


 Thanks a million,

This is something that has changed between Python 2 and Python 3. In
Python 2 what you tried is perfectly valid, but in Python 3 print has
become a function, so you have to write:

print(hello world!)

or

print('hello world!')

Happy New Year!



-- 
André Engels, andreeng...@gmail.com
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Re: [Tutor] 'Hello world'

[Alan Gauld]

Eldon L Mello Jr eldo...@hotmail.com wrote

programming and all but I honestly didn't expect I would have problems in 
my very first step which was just to print 'hello world'.



print hello world!

SyntaxError: invalid syntax (pyshell#1, line 1)


Looks like you are using a v2 tutorial, you need to find a v3 one.

There are several around, including my own - although it is not fully
complete all the basic topics are there now.
If you have experience in any other language the official one is
probably the best.

v3 of Python is a major rewrite and although largely backwardws compatible
there are a number of new features that are not. One of the most important
is print, but there are several others that will trip you up if you use a
v2 tutorial.

--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/ 



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[Tutor] Hello again. and another question.

[tsmundahl]

Hello Trask, 

I have been working on the first program. I got the files to read and print out 
the grades and averages, but when I write these files to the other txt file, 
all that I get is:

10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0

I know it is something simple. I am just not seeing it. Here is my code:



Grades = [ ]

filename = raw_input(Enter the filename with 10 grades to be averaged: )  
  

my_file_object = open (filename, r)

for a in range (10):
temp_string = my_file_object.readline()
Grades = Grades + [ float (temp_string)]

my_file_object.close()

for a in range (len(Grades)):
print Grade, str (a + 1) + :, Grades [a]

total = 0
for a in range (len(Grades)):
total = total + Grades[a]

average = total/float (len(Grades))

print The average grade was: , round(average,2)
print 
print Okay, we are assuming that you have created a file named 
'grade_file_2.txt' that is empty, yes?
print 

fname= raw_input(Please enter 'grade_file_2.txt' to write to new file: )

grades_file_2 = open(grade_file_2.txt, w)

for count in range (len(Grades)):
grades_file_2.write(str(%.2f% (len(Grades))) + \n)   
grades_file_2.close()

print 
print Nice Job. your file is done.


///



I am including the files. Let me know if you see anything goofy. 



Tom Mundahl




tm_week11_problem1.py
Description: Binary data
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
90.50
88.25
98.95
94.90
95.44
96.84
97.99
98.25
99.55
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Re: [Tutor] Hello again. and another question.

[Steve Willoughby]

On Thu, Oct 02, 2008 at 09:41:37PM +, [EMAIL PROTECTED] wrote:
 for count in range (len(Grades)):
 grades_file_2.write(str(%.2f% (len(Grades))) + \n)   
   

Look at what you're actually writing for each count.
See anything amiss there?


-- 
Steve Willoughby|  Using billion-dollar satellites
[EMAIL PROTECTED]   |  to hunt for Tupperware.
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Re: [Tutor] Hello again. and another question.

[Steve Willoughby]

You're doing a good job getting started with
programming here, keep getting the fundamentals
and then learn to refine those concepts over time.

But for future reference, here are some finer 
points for you to keep in mind to improve your
style and get a more Pythonic approach:

On Thu, Oct 02, 2008 at 09:41:37PM +, [EMAIL PROTECTED] wrote:
 Grades = [ ]

Usually we capitalize class and module names, but not
variables and functions/methods.  

 for a in range (10):
 temp_string = my_file_object.readline()
 Grades = Grades + [ float (temp_string)]

Might be more clear here to say

  Grades.append(float(temp_string))

instead of constructing a new list just to use +

You might also want to just read each line in the file
right in the for loop, which allows you to take ANY 
number of lines, not just 10, and makes the code
more concise at the same time:

for grade in my_file_object:
Grades.append(float(grade))

 for a in range (len(Grades)):
 print Grade, str (a + 1) + :, Grades [a]

If all you're going to do is to deal with each element
of a list in turn, instead of using an index over the
range of the number of elements, just directly iterate
over the list:

for a in Grades:
   print Grade:, a


And one GREAT habit to get into is to always be checking
if Python's built in functions and standard library already
offer something you're doing manually:

 total = 0
 for a in range (len(Grades)):
 total = total + Grades[a]
 
 average = total/float (len(Grades))


 average = sum(Grades) / len(Grades)


 fname= raw_input(Please enter 'grade_file_2.txt' to write to new file: )
 grades_file_2 = open(grade_file_2.txt, w)

I'm not sure why you're asking them to type in a file name
which you're ignoring and opening grade_file_2.txt anyway?

 for count in range (len(Grades)):
 grades_file_2.write(str(%.2f% (len(Grades))) + \n)   
 grades_file_2.close()

No need to explicitly call str() here, and I suspect print would
be clearer anyway.  And again, note the direct iteration over
Grades:

for grade in Grades:
print grades_file_2, %.2f % grade
grades_file_2.close()


-- 
Steve Willoughby|  Using billion-dollar satellites
[EMAIL PROTECTED]   |  to hunt for Tupperware.
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Re: [Tutor] Hello again. and another question.

[Alan Gauld]

[EMAIL PROTECTED] wrote


I got the files to read and print out the grades and averages,
but when I write these files to the other txt file, all that I get 
is:


10.0
10.0...
I know it is something simple. I am just not seeing it.


When the output doesn't vary like this you know you must be
writing the wrong value or the same value multiple times.

I'll add several comments on the code but the solution
is in there too...

Grades = [ ]
filename = raw_input(Enter the filename with 10 grades to be 
averaged: )


my_file_object = open (filename, r)
for a in range (10):
   temp_string = my_file_object.readline()
   Grades = Grades + [ float (temp_string)]
my_file_object.close()

for a in range (len(Grades)):
   print Grade, str (a + 1) + :, Grades [a]

##
# It would be better to just iterate over Grades:

for index, grade in enumerate(Grades):
   print Grade, index,:,grade

total = 0
for a in range (len(Grades)):
   total = total + Grades[a]

##
# same here:

for grade in Grades:
   total += grade

average = total/float (len(Grades))


##
# you don't need the float conversion here
because you converted them all to floats
at the beginning.

print The average grade was: , round(average,2)
print 
print Okay, we are assuming that you have created a file named 
'grade_file_2.txt' that is empty, yes?

print 

fname= raw_input(Please enter 'grade_file_2.txt' to write to new 
file: )

grades_file_2 = open(grade_file_2.txt, w)

for count in range (len(Grades)):
   grades_file_2.write(str(%.2f% (len(Grades))) + \n)

#
# Notice you are writing len(Grades) which is always 10 - your error!
But...

#
# and again the for loop, and simplify the output string:

for grade in Grades:
grades_file_2.write(%.2f\n % grade)

grades_file_2.close()



Python for loops are much more powerful when used
as foreach loops rather than always using indexing.

HTH,


--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld 



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[Tutor] Hello and some questions.

[tsmundahl]

Hello all. 

I recently starting taking Python in my state college. I joined the Python.org 
users group and I posted a couple of codes examples that I was having problems 
with, and I am wondering if there is anyone in this community that can help me. 
I did get some great advice on my previous posts however my code is still not 
working. I have two problems that I have to write code for. 

The first problem is a program that will take a list of ten grades from a user 
and then calculate the average of the ten numbers entered. The user can only 
use the numbers 1-10. Example. The total average of the grades you entered in 
was 5 which would be the average using number 1-10 in a sequence, but it needs 
to calculate an average no matter if the user puts in 3 5's and 7 10's. The 
average must be calculated. 

I did get some help in the python forums with this and I have come up the 
following, but I am getting a syntax error on the line that calls out total 
as a variable. Here is the code:

value = [ ]

for i in range(10):
range += 1
print (int(float(raw_input(Please enter a grade, use numbers 1 - 10: )))  
 
 
# getting a syntax error on this line
total = sum(value)

average = total/10.0
   
print The average sum of all of the grades that you entered is , (%.2f %  
average)


raw_input(\nPlease hit enter to quit.)

///The code does not work. 


The next problem is supposed to use the while loop. A user is supposed to enter 
some grade values. The user will continue to be prompted to enter grade values 
until the user has entered in  as  a grade value. Then the program is 
supposed to calculate the average of all of the grades entered including the 
. 

Here is my code, This code is not working either:

target = 

value = [ ]

while i in value  or not == target:
  i += 1
  print grade (int(float(raw_input(Please enter a grade: )))
 
  
total = sum(value)

average = total/target

print The average grade that you entered is , (%.2f % average)

raw_input(Please hit enter to exit.)


///Can anyone tell me what I am doing wrong on either of these problems? I know 
it is a logic error, but I am new to this so please bare with me. Again, thanks 
for your help. I am new to this forum so please have patience with me when I am 
posting. 

Thank you, 



Thomas Mundahl



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Re: [Tutor] Hello and some questions.

[Andre Engels]

On Mon, Sep 29, 2008 at 1:36 AM,  [EMAIL PROTECTED] wrote:

 I did get some help in the python forums with this and I have come up the 
 following, but I am getting a syntax error on the line that calls out total 
 as a variable. Here is the code:

The actual problem is in the previous line:

print (int(float(raw_input(Please enter a grade, use numbers 1 - 10: )))

If you count, there are 4 (s and 3 )s in there. Because every ( should
have a corresponding ) and vice versa, Python thinks that this
statement has not finished yet. It gives a syntax error at the _next_
line, because there it finds something that cannot be a correct
continuation of this statement.

However, even if you would do that, the result would still not be what
you want. It will give 0 each time, because value will always be the
empty list. Rather than printing out the grade that the user entered,
you would want to put it in the list value (an unlucky choice of a
name for a list of grades, in my opinion)

 The next problem is supposed to use the while loop. A user is supposed to 
 enter some grade values. The user will continue to be prompted to enter grade 
 values until the user has entered in  as  a grade value. Then the 
 program is supposed to calculate the average of all of the grades entered 
 including the .

 Here is my code, This code is not working either:

 target = 

 value = [ ]

 while i in value  or not == target:

That line will indeed cause Python to stumble. I'm not even sure what
you want to do here, so I can't really say what it should have been.

-- 
André Engels, [EMAIL PROTECTED]
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Re: [Tutor] Hello and some questions.

[Alan Gauld]

[EMAIL PROTECTED] wrote


The first problem is a program that will take a list of ten grades
from a user and then calculate the average

value = [ ]

for i in range(10):
   range += 1
   print (int(float(raw_input(Please enter a grade, use numbers 1 - 
10: )))


This is very confused.
First the range += 1 is going to be wierd because range is a
function and you are trying to add one to it! Don't use variable
names that are the same as built in functions.

Secondly you only need to convert the value to an int. You don't
need the float conversion as well.

Thirdly, as already pointed out you never assign the value anywhere
you just print it. You want to append it to your value list. (Also as 
a

general style point its a good idea to name collections as plurals
so use values instead of value - it just reads better)

And finally the source of the error, the mismatched parens.
Remember Python errors, especially syntax errorts, are often to be
found a line or two before where they are reported.



The next problem is supposed to use the while loop.
A user is supposed to enter some grade values...
continue to be prompted to enter grade values until
the user has entered in  as  a grade value.


calculate the average of all of the grades entered including the 
.


Really? How bizarre!


Here is my code, This code is not working either:

target = 

value = [ ]

while i in value  or not == target:


I have no idea what you intended here.
It doesn't read logically as a piece of Python
or math or even English...

If you remove the  sign it might make some sense as English,
although not as Python...

while i in value or not == target might be translated into Python as

while i in value or not i == target

or

while i in value or i != target

But in both cases its wrong since you are testing whether i
is in the list of values which is not part of the excercise.

It should just be

while i != target:

where wec assume i is the value input by the user.


 i += 1


But you don't want to increment i you want to get it from
the user, so

i = int(raw_input())

Same mistake as before: you are not storing the values
entered anywhere.


 print grade (int(float(raw_input(Please enter a grade: )))


And you haven't assigned anything to grade and you are simply
printing the input value rather than storing it in values


total = sum(value)
average = total/target


And this divides the total by  even if there are only 2 entries...
 was supposed to be the magic value used to stop the entry process
not a count of how many entries were made.


print The average grade that you entered is , (%.2f % average)


You need to read up on string formatting too. It should be:

print The average grade that you entered is %.2f % average


Can anyone tell me what I am doing wrong on either of
these problems? I know it is a logic error, but I am new


It's more than just logic errors you have some basic syntax
issues as well as failing to understand the concepts of
variables storing values during processing. print displays
but assignment(=) stores. And append() adds to a list...

HTH,

--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld 



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[Tutor] Hello

[Christopher Marlett]

Hi, I'm in a Python class and we were given the assignment to create our own 
graphic and my idea was to have a program that asks the user to click six 
points and then create a circle using the six points they clicked. Once they've 
done that I want eyes and a mouth to appear in the circle. I was wondering if 
that was possible or if I need to have them also click the points where the two 
eyes and nose should appear as well. I have the face written, it looks like 
this...
def main():
winWidth = 200  # give a name to the window width
winHeight = 150 #and height
win = GraphWin('Face', winWidth, winHeight) # give title and dimensions
win.setCoords(0, 0, winWidth, winHeight) # make right side up coordinates!

head = Circle(Point(40,100), 25) # set center and radius
head.setFill(yellow)
head.draw(win)

eye1 = Circle(Point(30, 105), 5)
eye1.setFill('blue')
eye1.draw(win)

eye2 = Line(Point(45, 105), Point(55, 105)) # set endpoints
eye2.setWidth(3)
eye2.draw(win)

mouth = Oval(Point(30, 90), Point(50, 85)) # set corners of bounding box
mouth.setFill(red)
mouth.draw(win)

message = Text(Point(winWidth/2, 20), 'Click anywhere to quit.')
message.draw(win)
win.getMouse()
win.close()

main()

I'm struggling with the Circle, however. This is what I have so far, but it 
won't work.

def main():
winWidth = 300
winHeight = 300
win = GraphWin('Draw a Circle', winWidth, winHeight)
win.setCoords(0, 0, winWidth, winHeight)
win.setBackground('yellow')
message = Text(Point(winWidth/2, 20), 'Click on six points')
message.draw(win)

# Get and draw six points of circle
p1 = win.getMouse()
p1.draw(win)
p2 = win.getMouse()
p2.draw(win)
p3 = win.getMouse()
p3.draw(win)
p4 = win.getMouse()
p4.draw(win)
p5 = win.getMouse()
p5.draw(win)
p6 = win.getMouse()
p6.draw(win)
points = [p1, p2, p3, p4, p5, p6]

# Use Oval object to draw the circle
Circle = Oval(points)
Circle.setFill('green')
Circle.setOutline('pink')
Circle.setWidth(4) # width of boundary line
Circle.draw(win)

# Wait for another click to exit
message.setText('Click anywhere to quit.')
message.setTextColor('red')
message.setStyle('italic')
message.setSize(20)
win.getMouse()
win.close()
Any advice you have would help out a lot. Thank you for your time. 
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Re: [Tutor] Hello

[Greg Graham]

It appears to me that the following line would not work:
Circle = Oval(points)

The variable points is a list of six points, and I don't know how one
would define a circle or oval with 6 points. At the top part of your
program, an oval is defined using two points, which makes sense. 

Maybe you should use two of the points for the outline of the face, one
point for each eye, and two for the mouth, which amounts to 6 points
total.

Greg


-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Christopher Marlett
Sent: Thursday, March 13, 2008 9:55 AM
To: tutor@python.org
Subject: [Tutor] Hello

Hi, I'm in a Python class and we were given the assignment to create our
own graphic and my idea was to have a program that asks the user to
click six points and then create a circle using the six points they
clicked. Once they've done that I want eyes and a mouth to appear in the
circle. I was wondering if that was possible or if I need to have them
also click the points where the two eyes and nose should appear as well.
I have the face written, it looks like this...
def main():
winWidth = 200  # give a name to the window width
winHeight = 150 #and height
win = GraphWin('Face', winWidth, winHeight) # give title and
dimensions
win.setCoords(0, 0, winWidth, winHeight) # make right side up
coordinates!

head = Circle(Point(40,100), 25) # set center and radius
head.setFill(yellow)
head.draw(win)

eye1 = Circle(Point(30, 105), 5)
eye1.setFill('blue')
eye1.draw(win)

eye2 = Line(Point(45, 105), Point(55, 105)) # set endpoints
eye2.setWidth(3)
eye2.draw(win)

mouth = Oval(Point(30, 90), Point(50, 85)) # set corners of bounding
box
mouth.setFill(red)
mouth.draw(win)

message = Text(Point(winWidth/2, 20), 'Click anywhere to quit.')
message.draw(win)
win.getMouse()
win.close()

main()

I'm struggling with the Circle, however. This is what I have so far, but
it won't work.

def main():
winWidth = 300
winHeight = 300
win = GraphWin('Draw a Circle', winWidth, winHeight)
win.setCoords(0, 0, winWidth, winHeight)
win.setBackground('yellow')
message = Text(Point(winWidth/2, 20), 'Click on six points')
message.draw(win)

# Get and draw six points of circle
p1 = win.getMouse()
p1.draw(win)
p2 = win.getMouse()
p2.draw(win)
p3 = win.getMouse()
p3.draw(win)
p4 = win.getMouse()
p4.draw(win)
p5 = win.getMouse()
p5.draw(win)
p6 = win.getMouse()
p6.draw(win)
points = [p1, p2, p3, p4, p5, p6]

# Use Oval object to draw the circle
Circle = Oval(points)
Circle.setFill('green')
Circle.setOutline('pink')
Circle.setWidth(4) # width of boundary line
Circle.draw(win)

# Wait for another click to exit
message.setText('Click anywhere to quit.')
message.setTextColor('red')
message.setStyle('italic')
message.setSize(20)
win.getMouse()
win.close()
Any advice you have would help out a lot. Thank you for your time. 
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[Tutor] hello can you help me solve this problem

[Christopher Marlett]

This may be a very broad question but whatever help you could give me would be 
great.

Exercise 2.4.5.1. * Make a program scene.py creating a scene with the graphics 
methods. You are likely to need to adjust the positions of objects by trial and 
error until you get the positions you want. Make sure you have graphics.py in 
the same directory as your program.

Exercise 2.4.5.2. * Elaborate your scene program so it becomes changeScene.py, 
and changes one or more times when you click the mouse (and use 
win.getMouse()). You may use the position of the mouse click to affect the 
result, or it may just indicate you are ready to go on to the next view. 

Also, I don't quite understand how this works. Do you e mail me with your 
response or is there a website I need to visit to see my question and your 
response posted?
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Re: [Tutor] hello can you help me solve this problem

[bob gailer]

Christopher Marlett wrote:
 This may be a very broad question but whatever help you could give me would 
 be great.

 Exercise 2.4.5.1. * Make a program scene.py creating a scene with the 
 graphics methods. You are likely to need to adjust the positions of objects 
 by trial and error until you get the positions you want. Make sure you have 
 graphics.py in the same directory as your program.

 Exercise 2.4.5.2. * Elaborate your scene program so it becomes 
 changeScene.py, and changes one or more times when you click the mouse (and 
 use win.getMouse()). You may use the position of the mouse click to affect 
 the result, or it may just indicate you are ready to go on to the next view. 
   
We don't offer solutions to homework for many reasons. I assume this is 
homework.

However if you show us a program (or even a program design) you've 
written and tell us where you are stuck we are glad to help.
 Also, I don't quite understand how this works. Do you e mail me with your 
 response or is there a website I need to visit to see my question and your 
 response posted?
   
We email you and the tutor list. Please reply to the list not just to 
the author.


-- 
Bob Gailer
919-636-4239 Chapel Hill, NC

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Re: [Tutor] hello can you help me solve this problem

[Alan Gauld]

Christopher Marlett [EMAIL PROTECTED] wrote

 Exercise 2.4.5.1. * Make a program scene.py creating a scene
 with the graphics methods. You are likely to need to adjust the
 positions of objects by trial and error until you get the positions
 you want. Make sure you have graphics.py in the same directory
 as your program.

Is this by any chance from the LiveWires tutorial?
If so they tend to use a lot of mod8ules that are specific
to their course so only folks with LiveWires experience
are likely to be able to help.

You need to give us some context as to where these come from
and where the graphics.py mentioned is found. Its not part of
the standard Python library.

Also it woyuld be good to tell us what part of the problem you
don't understand! The more specific the question the greater
the chance of an effective answer.

 Also, I don't quite understand how this works. Do you
 email me with your response or is there a website
 I need to visit to see my question and your response posted?

You mail themailing list and the server forwards it to everyone
on the list. We Reply All and the list server will forward the
reply to you and the list.

There are at least 3 web sites where you can read the messages
too, but a mail client is usually more powerful and faster.

Finally gmane do a news (nntp) feed that you can subscribe to
and receivecon your favoured news reader. In my view the best
of both worlds! :-)

HTH,

-- 
Alan Gauld
Author of the Learn to Program web site
Temorarily at:
http://uk.geocities.com/[EMAIL PROTECTED]/
Normally:
http://www.freenetpages.co.uk/hp/alan.gauld 


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Re: [Tutor] Hello and newbie question about self

[Tiger12506]

 I probably won't need to start writing classes but I really want to
 finish the book before I start coding something.

One of the greatest mistakes of my life was to completely finish a 
programming book before I started coding something. It is why I cannot write 
a Visual Basic program to this day, even though I read through an absolutely 
excellent book. I even said to myself, This will totally help me write 
Visual Basic programs as easily as I write Python programs. So instead, I 
learned C.

Always, always write code as you read a book. If it is a good 
book/programming language, you should be able to write working programs with 
increasing complexity as you continue in the book. Also, it is a good idea 
to periodically go back and observe code that you have written in the past 
and revise it to better reflect the skills you garner later. 

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[Tutor] Hello and newbie question about self

[Patrick]

Hi guru's,

New to the list. I bought O'Reilly's Learning Python (3rd edition for
2.5) a while back. Slowly making my way through it and was pleasantly
surprised that Python seems easier than C. Until...I bumped into the
self thingy.

Can anyone please point me to a document that explains self in
layman's terms. Or lacking such a doc throw in a much appreciated
layman's explanation what self is and when/where to use it? 

In the book (so far) I've seen self pop up in these examples (on pages
457 and 458):

class C1(C2, C3):
def setname(self, who)
self.name = who

class C1(C2, C3):
def __init__(self, who)
self.name = who

Thanks for any pointers!

Regards,
Patrick

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Re: [Tutor] Hello and newbie question about self

[Michael Langford]

In C, you may have objectorientedesque code like the following;

struct net {
int foo;
int bar;
int baz;
};


void populate_net( struct net* mynet, int fooval, int barval)
{
  mynet-foo = fooval;
  mynet-bar = barval;
  mynet -baz = fooval * 5;
}

int connect_to_net(struct net* mynet)
{
 return  open_internet_connection(mynet-foo);
}

int main (void)
{
  struct net inet;
  populate_net(inet,2,2);

  int returncode = connect_to_net(inet);
  printf(%d\n,returncode);
}

In that batch of C code, you manipulate the struct without fiddling
with its fields in the user code. You let the functions change its
values so that they are done correctly.

In python, you are doing something similar. However, they make some
syntactic sugar to make it so you don't have to pass the object in
explicily. That is what self is.

So the analgous python code is:


class net(object):
   def __init__(self,fooval,barbal):
   self.foo = fooval
   self.bar = barval
   self.baz = fooval*5

def connect_to(self):
   return open_internet_connection(self.foo)


inet = net(2,2)
returncode = inet.connect_to()
print returncode

See how you don't have to pass in the inet object in? Instead you call
it with the inet.connect_to() function, and the object itself is
passed in explicitly as self?

That's all it is.

Btw, make sure to always include self. Otherwise you'll be writing a
class method and it doesn't work the same way.

--Michael

On Feb 3, 2008 3:15 PM, Patrick [EMAIL PROTECTED] wrote:
 Hi guru's,

 New to the list. I bought O'Reilly's Learning Python (3rd edition for
 2.5) a while back. Slowly making my way through it and was pleasantly
 surprised that Python seems easier than C. Until...I bumped into the
 self thingy.

 Can anyone please point me to a document that explains self in
 layman's terms. Or lacking such a doc throw in a much appreciated
 layman's explanation what self is and when/where to use it?

 In the book (so far) I've seen self pop up in these examples (on pages
 457 and 458):

 class C1(C2, C3):
 def setname(self, who)
 self.name = who

 class C1(C2, C3):
 def __init__(self, who)
 self.name = who

 Thanks for any pointers!

 Regards,
 Patrick

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-- 
Michael Langford
Phone: 404-386-0495
Consulting: http://www.RowdyLabs.com
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Re: [Tutor] Hello and newbie question about self

[Kent Johnson]

Patrick wrote:
 Hi guru's,
 
 New to the list. I bought O'Reilly's Learning Python (3rd edition for
 2.5) a while back. Slowly making my way through it and was pleasantly
 surprised that Python seems easier than C. Until...I bumped into the
 self thingy.

This should be covered by any tutorial. 2nd edition of Learning Python 
has a section called Methods that introduces self. Also see
http://www.ibiblio.org/swaroopch/byteofpython/read/self.html
http://hetland.org/writing/instant-hacking.html

Kent
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Re: [Tutor] Hello and newbie question about self

[Alan Gauld]

Patrick [EMAIL PROTECTED] wrote 

 Can anyone please point me to a document that explains self in
 layman's terms. 

Try the OOP topic inmy tutorial...

 Or lacking such a doc throw in a much appreciated
 layman's explanation what self is and when/where to use it? 

Others have given code samples but a conceptuial explanation 
is that 
a) self is only used in OO programming within metjhods of a class.
b) self refers to the actual instance of the object receiving the 
message with caused the method to be invoked.

Thus if we have a class C with a method m and 3 instances 
a,b and z then when we invoke a.m() self will refer to a and 
when we invoke b.m() self will refer to b. This means that the 
innards of the method can use self to access the instance 
specific data for that invocation.

If you have used C++ at all you might recognise it as the 
same as 'this' in C++ except that in Python you must explicitly 
specify it whereas C++ creates 'this' magically behind the scenes.

See my tutorial for more on this under the heading 
Using classes.

If you haven't started writing classes yet, you can safely ignore 
it for now!


-- 
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld

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Re: [Tutor] Hello and newbie question about self

[Patrick Lists]

Hi Alan,

Alan Gauld wrote:
 Patrick [EMAIL PROTECTED] wrote 
 
 Can anyone please point me to a document that explains self in
 layman's terms. 
 
 Try the OOP topic inmy tutorial...

Thanks will have a look.

 Or lacking such a doc throw in a much appreciated
 layman's explanation what self is and when/where to use it? 
 
 Others have given code samples but a conceptuial explanation 
 is that 
 a) self is only used in OO programming within metjhods of a class.

Now that really helps. I was wondering about that and this answers it.

 b) self refers to the actual instance of the object receiving the 
 message with caused the method to be invoked.

This and reading chapter 23 in the book makes things much clearer now. 
Thanks!

 Thus if we have a class C with a method m and 3 instances 
 a,b and z then when we invoke a.m() self will refer to a and 
 when we invoke b.m() self will refer to b. This means that the 
 innards of the method can use self to access the instance 
 specific data for that invocation.

Even more clear now :)

 If you have used C++ at all you might recognise it as the 
 same as 'this' in C++ except that in Python you must explicitly 
 specify it whereas C++ creates 'this' magically behind the scenes.

Last time I used C++ was (iirc) in 1987 with a Borland product. I recall 
this and remember I got stuck on it then too.

 See my tutorial for more on this under the heading 
 Using classes.

Will do. Thanks for the pointer.

 If you haven't started writing classes yet, you can safely ignore 
 it for now!

I probably won't need to start writing classes but I really want to 
finish the book before I start coding something. I have a small script I 
did in (horrible) bash and look forward to try to implement it in (less 
horrible) Python.

Thanks for your help.

Regards,
Patrick



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Re: [Tutor] Hello and newbie question about self

[Patrick]

Hi Alan,

Alan Gauld wrote:
 Patrick [EMAIL PROTECTED] wrote 
 
 Can anyone please point me to a document that explains self in
 layman's terms. 
 
 Try the OOP topic inmy tutorial...

Thanks will have a look.

 Or lacking such a doc throw in a much appreciated
 layman's explanation what self is and when/where to use it? 
 
 Others have given code samples but a conceptuial explanation 
 is that 
 a) self is only used in OO programming within metjhods of a class.

Now that really helps. I was wondering about that and this answers it.

 b) self refers to the actual instance of the object receiving the 
 message with caused the method to be invoked.

This and reading chapter 23 in the book makes things much clearer now.
Thanks!

 Thus if we have a class C with a method m and 3 instances 
 a,b and z then when we invoke a.m() self will refer to a and 
 when we invoke b.m() self will refer to b. This means that the 
 innards of the method can use self to access the instance 
 specific data for that invocation.

Even more clear now :)

 If you have used C++ at all you might recognise it as the 
 same as 'this' in C++ except that in Python you must explicitly 
 specify it whereas C++ creates 'this' magically behind the scenes.

Last time I used C++ was (iirc) in 1987 with a Borland product. I recall
this and remember I got stuck on it then too.

 See my tutorial for more on this under the heading 
 Using classes.

Will do. Thanks for the pointer.

 If you haven't started writing classes yet, you can safely ignore 
 it for now!

I probably won't need to start writing classes but I really want to
finish the book before I start coding something. I have a small script I
did in (horrible) bash and look forward to try to implement it in (less
horrible) Python.

Thanks for your help.

Regards,
Patrick




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Re: [Tutor] Hello and newbie question about self

[Patrick]

Hi Michael,

Michael Langford wrote:
 In C, you may have objectorientedesque code like the following;
 
 struct net {
 int foo;
 int bar;
 int baz;
 };
 
 
 void populate_net( struct net* mynet, int fooval, int barval)
 {
   mynet-foo = fooval;
   mynet-bar = barval;
   mynet -baz = fooval * 5;
 }
 
 int connect_to_net(struct net* mynet)
 {
  return  open_internet_connection(mynet-foo);
 }
 
 int main (void)
 {
   struct net inet;
   populate_net(inet,2,2);
 
   int returncode = connect_to_net(inet);
   printf(%d\n,returncode);
 }

Heh I had to grab my C book and browse up on structs and pointers to get 
  an idea what this was all about :)

 In that batch of C code, you manipulate the struct without fiddling
 with its fields in the user code. You let the functions change its
 values so that they are done correctly.

Ok that makes sense.

 In python, you are doing something similar. However, they make some
 syntactic sugar to make it so you don't have to pass the object in
 explicily. That is what self is.

Got it.

 So the analgous python code is:
 
 
 class net(object):
def __init__(self,fooval,barbal):
self.foo = fooval
self.bar = barval
self.baz = fooval*5
 
 def connect_to(self):
return open_internet_connection(self.foo)
 
 
 inet = net(2,2)
 returncode = inet.connect_to()
 print returncode
 
 See how you don't have to pass in the inet object in? Instead you call
 it with the inet.connect_to() function, and the object itself is
 passed in explicitly as self?

Aaah starting to understand now.

 That's all it is.
 
 Btw, make sure to always include self. Otherwise you'll be writing a
 class method and it doesn't work the same way.

Thanks for the elaborate explanation!

Regards,
Patrick
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Re: [Tutor] Hello and newbie question about self

[Patrick]

Hi Kent,

Kent Johnson wrote:
 Patrick wrote:
 Hi guru's,

 New to the list. I bought O'Reilly's Learning Python (3rd edition for
 2.5) a while back. Slowly making my way through it and was pleasantly
 surprised that Python seems easier than C. Until...I bumped into the
 self thingy.
 
 This should be covered by any tutorial. 2nd edition of Learning Python 
 has a section called Methods that introduces self. Also see

Yes it does but all was not clear after I finished the first part 
(chapter 22 in my 3rd edition). Just read chapter 23 and things are 
clearer now. Luckily the start of chapter 24 mentions that it's no big 
deal if I didn't understand everything because they will dive deeper 
into it explaining more.

 http://www.ibiblio.org/swaroopch/byteofpython/read/self.html
 http://hetland.org/writing/instant-hacking.html

Thanks for the links. Will read them when I have some spare cycles.

Regards,
Patrick
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Re: [Tutor] Hello and newbie question about self

[Kent Johnson]

Tony Cappellini wrote:
 http://www.ibiblio.org/swaroopch/byteofpython/read/self.html
 Is there a typo in the contents of this web page?

Yes, you are right, C++ uses 'this'.

Kent

 
 Should this statement
 
 Note for C++/Java/C# Programmers
 
 The self in Python is equivalent to the self pointer in C++ and the
 this reference in Java and C#.
 
 
 Actually be
 
 Note for C++/Java/C# Programmers
 
 The self in Python is equivalent to the this pointer in C++ and the
 this reference in Java and C#.
 
 
 (I substituted this for self)
 

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