Re: [Tutor] Hi This is Michael Munn and I’m interested of the Python programming language.

[Mats Wichmann]

see also https://wiki.python.org/moin/PythonEditors

On August 26, 2018 5:19:20 PM MDT, Alan Gauld via Tutor  
wrote:
>On 26/08/18 18:42, Michael Munn wrote:
>
>> I’m using Python 3.6 and I heard a friend of mine told me that He
>write his
>> code using a word processer called Note pad plus some thing like that
>to
>> code.
>
>I assume you are on Windows OS?
>In which case you probably mean Notepad++ (like
>in the C++ programming language)
>
>It's a well known programmer's editor for Windows.
>
>Note that it is not a Word Processor, it has
>no support for formatting text (fonts, justification
>etc) it is just a powerful text editor, which is
>what you need for programming. Most importantly
>it saves in plain text not in a binary or XML/HTML
>format.
>
>> Any idea where to get this word Processer?
>
>A web search for Notepad++ should find it.
>However Python comes with a useful programming
>environment called Idle which you can use instead.
>It is Python specific whereas Notepad++ caters
>for many languages but if you are starting out
>in Python Idle is a fair choice and its already
>installed!
>
>I don't use Windows for Python work but last
>time I looked it was called something like
>Python GUI in the Windows start menu.
>
>> PS This question might sounds Stupid to you all.
>
>Not at all, choice of programming toolset is
>a very personal opinion and you will likely
>get several suggestions.
>
>> I ask you not to laugh at me if I post question like this in the
>future.
>We won't laugh, its why we are here.
>
>When posting questions always try to be as specific
>as possible, post any code you have and the full
>text of any error messages. Also post in plain text
>if possibly, email servers tends to mess up code
>otherwise.
>
>A reminder of your OS and Python version is also useful.
>
>Have fun,
>
>-- 
>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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-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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Re: [Tutor] Hi This is Michael Munn and I’m interested of the Python programming language.

[Alan Gauld via Tutor]

On 26/08/18 18:42, Michael Munn wrote:

> I’m using Python 3.6 and I heard a friend of mine told me that He write his
> code using a word processer called Note pad plus some thing like that to
> code.

I assume you are on Windows OS?
In which case you probably mean Notepad++ (like
in the C++ programming language)

It's a well known programmer's editor for Windows.

Note that it is not a Word Processor, it has
no support for formatting text (fonts, justification
etc) it is just a powerful text editor, which is
what you need for programming. Most importantly
it saves in plain text not in a binary or XML/HTML
format.

> Any idea where to get this word Processer?

A web search for Notepad++ should find it.
However Python comes with a useful programming
environment called Idle which you can use instead.
It is Python specific whereas Notepad++ caters
for many languages but if you are starting out
in Python Idle is a fair choice and its already
installed!

I don't use Windows for Python work but last
time I looked it was called something like
Python GUI in the Windows start menu.

> PS This question might sounds Stupid to you all.

Not at all, choice of programming toolset is
a very personal opinion and you will likely
get several suggestions.

> I ask you not to laugh at me if I post question like this in the future.
We won't laugh, its why we are here.

When posting questions always try to be as specific
as possible, post any code you have and the full
text of any error messages. Also post in plain text
if possibly, email servers tends to mess up code
otherwise.

A reminder of your OS and Python version is also useful.

Have fun,

-- 
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] Hi This is Michael Munn and I’m interested of the Python programming language.

[Michael Munn]

Hi All, This is Michael and I have a question about resources on starting
to code python.
I’m using Python 3.6 and I heard a friend of mine told me that He write his
code using a word processer called Note pad plus some thing like that to
code.
Any idea where to get this word Processer?
Please respond if you all get any chance.
Best Regards
Michael Munn
PS This question might sounds Stupid to you all.  I just want you all  to
know that I’m a beginner Pythonist. And I know Nothing about coding at all.
I ask you not to laugh at me if I post question like this in the future.
Thanks and have a nice day.
Best REGARDS
michael Munn
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Re: [Tutor] Hi there, have a question for a side project in physics.....

[Steven D'Aprano]

On Mon, Dec 25, 2017 at 09:45:35AM +, Alan Gauld via Tutor wrote:
> On 25/12/17 09:08, Siddharth Sehgal wrote:
> 
> >physics masters student. I am trying to use the Sellmeier Equation
> 
> >I originally state them as floats. However such a process apparently  > 
> >cannot be done with "floats" like these.
> 
> It can be done just with a large error (although as a physics
> grad you will know how to calculate the error I assume)

I don't think the numbers or equation is so ill-conditioned that the 
error will be "large", or at least not larger than the experimental 
uncertainty in the coefficients.

Floating point maths is tricky, but it isn't *that* tricky. Especially 
not for "reasonable" sized numbers, with only nine or ten significant 
figures. This is the huge advantage of IEEE-754 maths using 64-bit 
floats, as Python does: most of the time, the obvious formula "just 
works".



-- 
Steve
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Re: [Tutor] Hi there, have a question for a side project in physics.....

[Steven D'Aprano]

On Mon, Dec 25, 2017 at 01:08:13PM +0400, Siddharth Sehgal wrote:

> The actual equation is below screen shotted

No it isn't -- either you forgot to attach it, or the mailing list 
removed it.

Do you mean this equation?

https://en.wikipedia.org/wiki/Sellmeier_equation


I suggest you try using Python and compare your results to those from 
here:

http://www.calctool.org/CALC/phys/optics/sellmeier

or from some authoritative source of refractive indexes.


Here is my simple test, for borosilicate glass BK7 using the values from 
Wikipedia. Using the website:

refractive index at 590 nm = 1.51670

Using Python, I get: 1.516698697993053

Here is my code. Feel free to use it for any purpose, no credit required 
(except as needed to meet any academic obligations you may have about 
collaboration and/or plagiarism).


import math

def sellmeier(lambd, B1, B2, B3, C1, C2, C3):
return 1 + B1*f(lambd, C1) + B2*f(lambd, C2) + B3*f(lambd, C3)

def f(x, y):
x2 = x**2
return x2/(x2 - y)


# Coefficients for BK7 (borosilicate crown glass)

result = sellmeier(0.590, # 590nm == 0.590µm
  1.03961212,
  0.231792344,
  1.01046945,
  6.00069867e-3,
  2.00179144e-2,
  103.560653)

print(math.sqrt(result))




-- 
Steve
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Re: [Tutor] Hi there, have a question for a side project in physics.....

[Steven D'Aprano]

On Mon, Dec 25, 2017 at 01:08:13PM +0400, Siddharth Sehgal wrote:
> Hi there
> 
> 
> I am a novice python user and am a physics masters student. I am 
> trying to use the Sellmeier Equation to calculate a refractive index. 
> The coefficients of this equation are decimals to a large number of 
> sig figs ( i.e B1 = 1.03961212, B2 = 0.231792344, C1 = 6.00069867×10−3 

That's not really a lot of significant figures. Python floats are C 
64-bit doubles, so they can represent about 15 or 16 significant 
figures. The numbers you show are only 9 or 10.


> ... and so on) in the sellmeier formula there is a lot of fractions, 
> multiplication and squaring of these numbers. I originally state them 
> as floats. However such a process apparently cannot be done with 
> "floats" like these.

What makes you think that you cannot use floats for this?

Of course floating point maths on computers is not the same as real 
arithmetic of the Real numbers in mathematics class, and you may need to 
carefully consider the possible error conditions in your equations, 
round-off error, and so forth, but in general I would expect that simply 
using Python as a calculator will be fine for all but the most precise 
calculations.

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Re: [Tutor] Hi there, have a question for a side project in physics.....

[Alan Gauld via Tutor]

On 25/12/17 09:08, Siddharth Sehgal wrote:


physics masters student. I am trying to use the Sellmeier Equation



I originally state them as floats. However such a process apparently  > cannot be done 
with "floats" like these.


It can be done just with a large error (although as a physics
grad you will know how to calculate the error I assume)


What do i do? PLEASE NEED HELP!


There ae several ways and I guess the best will involve using 
SciPy/numpy features.

But since i don't know those I'll suggest the old school way
which is to multiply your numbers up until they become integers
and take advantage of pythons big int feature. You will need
to plug all the multipliers into your formula and work out
the final multiplier - but that is just exponent arithmetic
so should be doable. Finally adjust your answer by the
calculated exponent.

As I say there will probably be better solutions in the
numpy space and hopefully someone else will tell you about
them.


The actual equation is below screen shotted


This list does not permit non-text attachments - the server
throws them away.

Alan G.

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[Tutor] Hi there, have a question for a side project in physics.....

[Siddharth Sehgal]

Hi there


I am a novice python user and am a physics masters student. I am trying to use 
the Sellmeier Equation to calculate a refractive index. The coefficients of 
this equation are decimals to a large number of sig figs ( i.e B1 = 1.03961212, 
B2 = 0.231792344, C1 = 6.00069867×10−3 ... and so on) in the sellmeier formula 
there is a lot of fractions, multiplication and squaring of these numbers. I 
originally state them as floats. However such a process apparently cannot be 
done with "floats" like these. What do i do? PLEASE NEED HELP!

The actual equation is below screen shotted


Many thanks, I look forward to your response, 

THIS IS NOT HOMEWORK BY THE WAY, I just want to use this program as it saves a 
lot of writing on paper. 


Siddharth Sehgal 
MSc Student in Physics 

SUNY - Stony Brook University 

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Re: [Tutor] Hi all: How do I save a file in a designated folder?

[Alan Gauld via Tutor]

On 03/05/17 00:28, Cameron Simpson wrote:

>> And so forth? I assume you mean
>>
>> MMDD.png format?
>>
>> You should read about the strftime function in the time
> 
> Further to this, I would also advocate that you consider writing the 
> timestamp 
> from largest unit to smallest unit, like an ISO8601 timestamp, which 
> typically 
> looks like:
> 
>   MMDD.png

Yes, I absolutely second this advice and should have included it.
ISO dates make programming life so much easier!


-- 
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] Hi all: How do I save a file in a designated folder?

[eryk sun]

On Tue, May 2, 2017 at 6:09 PM, Michael C
 wrote:
> screenshot.save("\test\missed.png")

You probably know that "\t" represents a tab in a string literal, but
there's something about working with a path that causes people to
overlook this. Windows won't overlook it. Control characters, i.e.
characters with an ordinal value below 32, are forbidden in Windows
file names.

Also, you're depending on whatever drive or UNC path is the current
directory. For example:

>>> os.chdir('C:\\')
>>> os.path.abspath('/test/missed.png')
'C:\\test\\missed.png'

>>> os.chdir('localhost\C$')
>>> os.path.abspath('/test/missed.png')
'localhost\\C$\\test\\missed.png'

A fully-qualified path must start with the drive or UNC share. For example:

>>> os.path.abspath('C:/test/missed.png')
'C:\\test\\missed.png'

>>> os.path.abspath('//localhost/C$/test/missed.png')
'localhost\\C$\\test\\missed.png'

In this case I'm using abspath() to normalize the path, which first
has Windows itself normalize the path via GetFullPathName(). This
shows what Windows will actually try to open or create, given that it
implements legacy DOS rules. For example, it ignores trailing spaces
and dots in the final path component:

>>> os.path.abspath('C:/test/missed.png ... ')
'C:\\test\\missed.png'

and DOS devices are virtually present in every directory:

>>> os.path.abspath('C:/test/nul.txt')
'.\\nul'
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Re: [Tutor] Hi all: How do I save a file in a designated folder?

[Cameron Simpson]

On 03May2017 00:01, Alan Gauld  wrote:

On 02/05/17 19:09, Michael C wrote:

1. How to name the file with time stamp.   e.g.   05012017.png and so forth.


And so forth? I assume you mean

MMDD.png format?

You should read about the strftime function in the time
(and datetime) module. Other functions thee will find
the current date/time for you. Thee are examples on the
documentation pages but if you get stuck come back
with specific questioons.


Further to this, I would also advocate that you consider writing the timestamp 
from largest unit to smallest unit, like an ISO8601 timestamp, which typically 
looks like:


 MMDD.png

See:
 https://www.iso.org/iso-8601-date-and-time-format.html
 https://en.wikipedia.org/wiki/ISO_8601

This has the advantage that a lexical sort (as in a typical directory listing 
or file glob) automatically arranges names in date order.


I'd also remark that the USA centric format (MMDD) that Alan inferred is 
particularly unfortunate in that (a) the rest of the world generally use 
DDMM so that the units come in increasing size and (b) doesn't sort very 
nicely at all. Of course, you might have meant 5th December 2017 above, so who 
knows? But the very ambiguity makes this one to avoid.


For numeric timestamps like yours I only ever use MMDD (or the obvious 
variants like -MM-DD etc). If I use another, I make the month a word (lousy 
for sorting and parsing, but clear to the human reader); I only do that in 
prose, not in filenames.


Cheers,
Cameron Simpson 
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Re: [Tutor] Hi all: How do I save a file in a designated folder?

[Alan Gauld via Tutor]

On 02/05/17 19:09, Michael C wrote:
> from PIL import Image
> from PIL import ImageGrab
> 
> screenshot = ImageGrab.grab()
> screenshot.show()
> screenshot.save("\test\missed.png")
> 
> This is my current code, using Python Image Library!

You should probably investigate Pillow, I believe
development of PIL has now ceased in favour of Pillow.
Pillow is backwardly compatible with PIL so your
existing code should still work.

> What I would like to get help with is:
> 
> 1. How to name the file with time stamp.   e.g.   05012017.png and so forth.

And so forth? I assume you mean

MMDD.png format?

You should read about the strftime function in the time
(and datetime) module. Other functions thee will find
the current date/time for you. Thee are examples on the
documentation pages but if you get stuck come back
with specific questioons.

> 2. How to save it in a designated folder like  C:\test\test2\ and so forth.

That is just string handling. thee is nothing special
about a file path(*), it is just a string. Store the folder as one
string then construct your file path with

filepath = folder + filename

(*)Having said that there is nothing special there is a
dedicated module for working with paths - os.path - that
has convenience functions for constructing and
de-constructing path strings. You might find it useful.

> P.S. I am on windows 10

The biggest issue with Windows is its use of \ as a separator.
Be sure to use raw strings ( ie prefix an r: r'') or just
use a Unix style [path with / instead of \. Or use os.path
which will intelligently decide which separator to use.

HTH
-- 
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] Hi all: How do I save a file in a designated folder?

[Michael C]

from PIL import Image
from PIL import ImageGrab

# takes the screenshot
screenshot = ImageGrab.grab()
# display the screenshot
screenshot.show()
# save the screenshot
screenshot.save("\test\missed.png")



This is my current code, using Python Image Library!

What I would like to get help with is:

1. How to name the file with time stamp.   e.g.   05012017.png and so forth.
2. How to save it in a designated folder like  C:\test\test2\ and so forth.

P.S. I am on windows 10


Thanks!
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Re: [Tutor] Hi

[Walter Prins]

Hi,

On 23 June 2016 at 19:00, Bharath Swaminathan  wrote:
> Can I run my python code in multiple processors? I have a dual core...

Like an idiot I forgot a link for the "pp" module, my apologies.  Here it is:

http://www.parallelpython.com/

If you have/use pip, you can simply enter (from an operating system
shell/command prompt, and provided you've got an internet connection):

pip2 install pp


Walter
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Re: [Tutor] Hi

[Walter Prins]

Hi Bharath,

On 23 June 2016 at 19:00, Bharath Swaminathan  wrote:
>
> Can I run my python code in multiple processors? I have a dual core...


Notwithstanding Alan's answer, I'm going to directly answer your
question: Yes, it can.

However  The degree and level of success you're going to have in
fully utilising your dual cores (in other words parallelizing your
Python program) are going to depend on the concurrency mechanism you
choose.

As a minor digression: Concurrency and Parallelism are not the same
thing, though they're related.  Concurrency "is about dealing with a
lot of things at once" (e.g. it's about design, it's about structure)
whereas parallelism "is about doing a lot of things at once" (e.g.
it's about execution)[1]  Please go watch the referenced video if this
is at all unclear as it's actually and important distinction IMO.  As
an additional reference Russel Winder has given several talks over the
years on threads, parallelism, concurrency and related topics which
are well worth watching, please google around as I can't lay my hands
on one I saw at Pycon which was particularly good.  The following page
seems to contain some useful links:[2] -- The one I saw was the "GIL
isn't evil" presentation IIRC.

Anyway, so, most people reach for threads as the default concurrency
construct.  Now, Python also supports threads (see the "threading"
module: https://www.youtube.com/watch?v=cN_DpYBzKso) and you could use
this as concurrency construct, but depending on what your program does
you will likely find that it doesn't fully make use of your 2 cores
like you want to.  This is down to the design of the Python
interpreter, and something called the Global Interpreter Lock (GIL).
In most cases the GIL essentially has the result of serializing most
of the execution of multiple thread, resulting in sub-optimal use of
processor resources, when using real thread.

For this reason multi-processing is highly preferable for Python and
will allow you to effectively sidestep the GIL and make full use of
all your cores (or even multiple machines if you want).  The
"multiprocessing" module
(https://docs.python.org/2/library/multiprocessing.html) provides an
API similar to that of the "threading" module but works with processes
and is perhaps worth looking at.

For other concurrency approaches, frameworks and libraries, you may
want to look at https://wiki.python.org/moin/Concurrency/  There are
quite a few.

I want to highlight one particular Python concurrency module, called
"ParrallelPython", the module name being "pp", which I've had great
success with and highly recommend if your problem is suitable to it.
The beauty of this module is that it automatically load balances
according to the relative speeds of the processors/cores available.
and can easily scale if more compute cores are added.  So you can very
easily also just spin up more nodes and providing they're suitable
equipped with a "pp" based server will join and share the
computational load regardless of the relative speeds/cores on each
machine/processor.  All the work just gets split equally based on
relative speed.  Really rather easy and satisfying to see and use.

(Oh and by the way, "pp" also works seamless with PyPy, which in the
stuff I did sped the programs up several orders of magnitude, should
you need even more speed.  If you don't know what PyPy is:  PyPy is an
alternative Jit-compiler version of Python. Basically your Python
programs are compiled to machine code on the fly as they run and will
in many cases, depending on what they're doing, be in some cases
/several orders of magnitude/ faster than the same code on the C
Python interpreter.)

Anyway, that's enough for now.  Have fun and ask again if anything's unclear.

Walter




[1] Rob Pike - 'Concurrency Is Not Parallelism',
https://www.youtube.com/watch?v=cN_DpYBzKso
[2] Presentations Relating to
Parallelism,http://www.concertant.com/presentations_parallelism.html
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Re: [Tutor] Hi

[Alan Gauld via Tutor]

On 23/06/16 19:00, Bharath Swaminathan wrote:
> Can I run my python code in multiple processors? I have a dual core...

Your OS may run your python code on multiple processors but
it's not something you can easily control in Python. Remember
that your computer probably has hundreds of processes running
at any one time and your python program(s) will only be a part
of the total load. The OS schedules the jobs to run on whichever
processor is available at any given time - it may well
use different processors for the same process during the
lifetime of that process.

Now, if what you really want to know is whether the OS can
split a single Python process over multiple CPU cores in
parallel, that's a much more complex question and I think
the current answer is probably not. (But others on this list
know a lot more about that kind of thing than I do!)  But
it depends on the exact version of Python you are running
and probably which OS you are using too.

In my experience trying to guess how the OS will schedule
your jobs is an exercise in frustration. Let the OS do its
thing and only worry about those kinds of optimisation once
you have proved it is really an issue (by measurement).


-- 
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] Hi

[Bharath Swaminathan]

Can I run my python code in multiple processors? I have a dual core...
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[Tutor] Hi Dear!

[Alexa kun]

Hi Dear!
I newbie and read 2.1.2. Interactive Mode
https://docs.python.org/3/tutorial/interpreter.html

but when I type

>>> the_world_is_flat = True
>>> if the_world_is_flat:
... print("Be careful not to fall off!")

I got answer

IndentationError: expected an indented block

[root@localhost /]# python3
Python 3.4.3 (default, Jun 29 2015, 12:15:26)
[GCC 5.1.1 20150618 (Red Hat 5.1.1-4)] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>> the_world_is_flat = True
>>> if the_world_is_flat:
... print(Be careful not to fall off!)
  File "", line 2
print(Be careful not to fall off!)
^
IndentationError: expected an indented block
>>>

I have installed Python3 in Linux Fedora 23
Please tell my why Python3 doesn't work?

Sincerely!
Alexander
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Re: [Tutor] Hi Dear!

[Joel Goldstick]

On Thu, Feb 4, 2016 at 7:49 AM, Alexa kun  wrote:

> Hi Dear!
> I newbie and read 2.1.2. Interactive Mode
> https://docs.python.org/3/tutorial/interpreter.html
>
> but when I type
>
> >>> the_world_is_flat = True
> >>> if the_world_is_flat:
> ... print("Be careful not to fall off!")
>
> I got answer
>
> IndentationError: expected an indented block
>
> [root@localhost /]# python3
> Python 3.4.3 (default, Jun 29 2015, 12:15:26)
> [GCC 5.1.1 20150618 (Red Hat 5.1.1-4)] on linux
> Type "help", "copyright", "credits" or "license" for more information.
>
> >>> the_world_is_flat = True
> >>> if the_world_is_flat:
> ... print(Be careful not to fall off!)
>   File "", line 2
> print(Be careful not to fall off!)
> ^
> IndentationError: expected an indented block
> >>>
> There is something funny about your print function.  The three periods
> indicate that you are no longer in interactive mode.
>

See my session below


> I have installed Python3 in Linux Fedora 23
> Please tell my why Python3 doesn't work?
>
> Sincerely!
> Alexander
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>>> flat = True
>>> if flat:
... print("flat")
...
flat
>>>


-- 
Joel Goldstick
http://joelgoldstick.com/stats/birthdays
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Re: [Tutor] Hi Dear!

[Steven D'Aprano]

Hello Alexander, and welcome!

My answers are below, between your questions (starting with > quote 
marks).


On Thu, Feb 04, 2016 at 02:49:39PM +0200, Alexa kun wrote:
> Hi Dear!
> I newbie and read 2.1.2. Interactive Mode
> https://docs.python.org/3/tutorial/interpreter.html
> 
> but when I type
> 
> >>> the_world_is_flat = True
> >>> if the_world_is_flat:
> ... print("Be careful not to fall off!")

Look carefully at the last line. Do you notice the indented space 
between the three dots ... and the print? You need to either press space 
at least once, or the TAB key, to indent the line.



> I got answer
> 
> IndentationError: expected an indented block

Here Python tells you exactly what the problem is. Python expected an 
indented block of text (at least one line, indented by at least one 
space), but you didn't indent the line.


Python expects:

if the_world_is_flat:
print(Be careful not to fall off!)


but you typed:

if the_world_is_flat:
print(Be careful not to fall off!)


without the indentation. You should press the TAB key to indent, or the 
SPACE key at least once.



Also, one last comment:

> [root@localhost /]# python3

I see from this that you are running Python as the root superuser. This 
is VERY dangerous for a beginner (and even for an expert). As root, you 
can over-write essential system files. Which means that if you 
accidentally give the wrong Python commands, you could break your system 
and leave it in a broken state where it needs to be re-installed.

It is MUCH safer to experiment as the regular user. If the command 
prompt shows # then you are running as root. If it shows $ then you are 
running as a regular user.



-- 
Steve
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Re: [Tutor] Hi Dear!

[Alan Gauld]

On 04/02/16 12:49, Alexa kun wrote:
> Hi Dear!

Hi.
Can I ask that in future you choose a subject line that reflects your
question?
For this case it might be "IndentationError" say.

> but when I type
> 
 the_world_is_flat = True
 if the_world_is_flat:
> ... print("Be careful not to fall off!")

The problem is that is not what you typed.
And this is why we always ask for the full error
trace - thanks for including it.

 if the_world_is_flat:
> ... print(Be careful not to fall off!)
>   File "", line 2
> print(Be careful not to fall off!)
> ^
> IndentationError: expected an indented block

It says that there is an IndentationError which means that
Python is expecting to see a line starting in a different
place from where it does. In your case that means the line
after the 'if' is expected to be "indented". That is it
should have a few spaces in front of it (we usually
recommend 4 but Python doesn't care so long as there
is more than the preceding line).

The indentation is Python's way of telling which bits of
code need to be executed if the 'if' test is true. Anything
that is indented will be executed (or missed if the test
is false) as appropriate. The indentation needs to be the
same for all the indented lines.

ie

if foo > 42:
   print (foo)
   f = 666

is ok but

if foo > 42:
print (foo)
  f00 = 666# not enough spaces

won't work.

> Please tell my why Python3 doesn't work?

It's working just fine, you only need to give it
some space(s)... :-)

-- 
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] Hi Dear!

[Emil Natan]

On Thu, Feb 4, 2016 at 2:49 PM, Alexa kun  wrote:

> Hi Dear!
> I newbie and read 2.1.2. Interactive Mode
> https://docs.python.org/3/tutorial/interpreter.html
>
> but when I type
>
> >>> the_world_is_flat = True
> >>> if the_world_is_flat:
> ... print("Be careful not to fall off!")
>
> I got answer
>
> IndentationError: expected an indented block
>
> [root@localhost /]# python3
> Python 3.4.3 (default, Jun 29 2015, 12:15:26)
> [GCC 5.1.1 20150618 (Red Hat 5.1.1-4)] on linux
> Type "help", "copyright", "credits" or "license" for more information.
>
> >>> the_world_is_flat = True
> >>> if the_world_is_flat:
> ... print(Be careful not to fall off!)
>   File "", line 2
> print(Be careful not to fall off!)
> ^
> IndentationError: expected an indented block
> >>>
>
>

You should have the print function indented, usually by 4 spaces. This is
how Python knows which commands to be executed as part of the if block. So
this is what you'll make your code work:

 >>> the_world_is_flat = True
>>> if the_world_is_flat:
... print("Be careful not to fall off!")
...
Be careful not to fall off!

The interpreter also tries to help you, it puts ... at the begging of the
line (instead of >>>) which means it expect some indentation.

Emil

I have installed Python3 in Linux Fedora 23
> Please tell my why Python3 doesn't work?
>
> Sincerely!
> Alexander
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Re: [Tutor] Hi Tutor

[Martin A. Brown]

>I wrote this short program for my grandson:
>
>from random import sample
>
>soups = ['Onion soup', 'Veggie soup', 'Chicken soup', 'Corn soup']
>salads = ['Veggie', 'Onion', 'Cabbage', 'Lettuce', 'Caesar', 'Tomato']
>main = ['Crab cake', 'Catfish', 'Ribs', 'Chopped liver', 'Meat balls']
>beverage = ['Wine', 'Rum', 'Lemonade', 'Red bull', 'Margarita', 'Jin']
>
>def dish(soups):
>return (sample(soups, 1))
>
>print('Soup:\t\t', dish(soups))
>print('Salad:\t\t', dish(salads))
>print('Main dish:\t', dish(main))
>print('Beverage:\t', dish(beverage))
>
>A possible output could be:
>
>Soup: ['Chicken soup']
>Salad: ['Caesar']
>Main dish: ['Meat balls']
>Beverage: ['Wine']
>
>How do I get rid from the square brackets and the quotation marks 
>in the output?

There are many possible answers to this question.  Here's my answer:

  from random import choice

  def dish(options):
  return choice(options)

Then, the function dish() will return exactly one element from the 
options.  Since each of soup, salads, main and beverage are lists 
with string elements, the dish() function will return a string.

I would like to have some Onion soup, the Crab cake, Rum and a 
Caesar, please.

Good luck,

-Martin

-- 
Martin A. Brown
http://linux-ip.net/
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[Tutor] Hi Tutor

[yehudak .]

I wrote this short program for my grandson:

from random import sample

soups = ['Onion soup', 'Veggie soup', 'Chicken soup', 'Corn soup']
salads = ['Veggie', 'Onion', 'Cabbage', 'Lettuce', 'Caesar', 'Tomato']
main = ['Crab cake', 'Catfish', 'Ribs', 'Chopped liver', 'Meat balls']
beverage = ['Wine', 'Rum', 'Lemonade', 'Red bull', 'Margarita', 'Jin']

def dish(soups):
return (sample(soups, 1))

print('Soup:\t\t', dish(soups))
print('Salad:\t\t', dish(salads))
print('Main dish:\t', dish(main))
print('Beverage:\t', dish(beverage))

A possible output could be:

Soup: ['Chicken soup']
Salad: ['Caesar']
Main dish: ['Meat balls']
Beverage: ['Wine']

How do I get rid from the square brackets and the quotation marks in the
output?

Thank you.
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Re: [Tutor] Hi there,

[Alan Gauld]

On 02/01/16 12:45, yehudak . wrote:


> I know the mathematical way to solve it (resulting in 24), but I want a
> Python solution.

Show us your code.

Usually "the mathematical way to do it" works in Python too.
Although there will likely be other ways that may sometimes
run faster or easier to code.

But until we see your code we can't comment on what you
are doing.

One way to try would be continually dividing by 10 until you
get a non-zero remainder. Count the number of divisions
necessary. Hint: The divmod() function may help here.

-- 
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] Hi there,

[Steven D'Aprano]

On Sat, Jan 02, 2016 at 02:45:30PM +0200, yehudak . wrote:
> I'm trying to write a Python 3.5 program to find how many trailing zeros
> are in 100! (factorial of 100).
> I downloaded factorial from Math module, but all my efforts to solve the
> problem failed.
> 
> I know the mathematical way to solve it (resulting in 24), but I want a
> Python solution.

Here are the steps needed:

http://www.purplemath.com/modules/factzero.htm

Try writing some Python code for this, and if you have trouble, show us 
your code and we'll help. But you have to write it first -- we won't do 
your homework for you.



-- 
Steve
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[Tutor] Hi there,

[yehudak .]

I'm trying to write a Python 3.5 program to find how many trailing zeros
are in 100! (factorial of 100).
I downloaded factorial from Math module, but all my efforts to solve the
problem failed.

I know the mathematical way to solve it (resulting in 24), but I want a
Python solution.

Thank you.
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[Tutor] Hi pyusb Cant Connect Hid Device !

[Seint Aksoy]

Hello i ve searching some information for my problem .
i m trying to write data to usb hid device
idVendor=0x0123, idProduct=0x0012
its pic18f2550


Bus 001 Device 008: ID 0123:0012
Device Descriptor:
  bLength18
  bDescriptorType 1
  bcdUSB   1.10
  bDeviceClass0 (Defined at Interface level)
  bDeviceSubClass 0
  bDeviceProtocol 0
  bMaxPacketSize064
  idVendor   0x0123
  idProduct  0x0012
  bcdDevice1.00
  iManufacturer   1 USB
  iProduct2 IO INTERFACE
  iSerial 0
  bNumConfigurations  1
  Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength   41
bNumInterfaces  1
bConfigurationValue 1
iConfiguration  0
bmAttributes 0xc0
  Self Powered
MaxPower  100mA
Interface Descriptor:
  bLength 9
  bDescriptorType 4
  bInterfaceNumber0
  bAlternateSetting   0
  bNumEndpoints   2
  bInterfaceClass 3 Human Interface Device
  bInterfaceSubClass  0 No Subclass
  bInterfaceProtocol  0 None
  iInterface  0
HID Device Descriptor:
  bLength 9
  bDescriptorType33
  bcdHID   1.00
  bCountryCode0 Not supported
  bNumDescriptors 1
  bDescriptorType34 Report
  wDescriptorLength  32
  Report Descriptor: (length is 32)
Item(Global): Usage Page, data= [ 0x00 0xff ] 65280
(null)
Item(Local ): Usage, data= [ 0x01 ] 1
(null)
Item(Main  ): Collection, data= [ 0x01 ] 1
Application
Item(Local ): Usage Minimum, data= [ 0x01 ] 1
(null)
Item(Local ): Usage Maximum, data= [ 0x08 ] 8
(null)
Item(Global): Logical Minimum, data= [ 0x80 ] 128
Item(Global): Logical Maximum, data= [ 0x7f ] 127
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Global): Report Count, data= [ 0x02 ] 2
Item(Main  ): Input, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile
Bitfield
Item(Local ): Usage Minimum, data= [ 0x01 ] 1
(null)
Item(Local ): Usage Maximum, data= [ 0x08 ] 8
(null)
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Global): Report Count, data= [ 0x02 ] 2
Item(Main  ): Output, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile
Bitfield
Item(Main  ): End Collection, data=none
  Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81  EP 1 IN
bmAttributes3
  Transfer TypeInterrupt
  Synch Type   None
  Usage Type   Data
wMaxPacketSize 0x0008  1x 8 bytes
bInterval 250
  Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01  EP 1 OUT
bmAttributes3
  Transfer TypeInterrupt
  Synch Type   None
  Usage Type   Data
wMaxPacketSize 0x0008  1x 8 bytes
bInterval  10
Device Status: 0x0001


i ve tried kind of codes
read_bytes = self.handle.interruptRead(0x81, 8, 1000)

hid_device.write(0x1, ([0x91]))

both is return len(data)
so it should write but its not writing !
is there anyone can help me thank you!
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Re: [Tutor] Hi pyusb Cant Connect Hid Device !

[Alan Gauld]

On 21/12/15 03:36, Seint Aksoy wrote:
> Hello i ve searching some information for my problem .
> i m trying to write data to usb hid device

This list if for learning the core python language and standard
library. Pyusb is not part of that and a bit more technical
than our normal scope. You would be better asking on a pyusb
support forum, or failing that on the main Python mailing list/newsgroup.

The pyusb list details are here:
https://lists.sourceforge.net/lists/listinfo/pyusb-users


-- 
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] Hi

[Vick]

 

Hello

 

I've been using Python 27 on Windows for as long as I have used a computer
for intelligent purposes, viz. since 2000 I think, well the earlier versions
till the current version I'm using now. I used it primarily for mathematical
precision on numerical computations. I make my own codes. I'm fluent in it
and in VBA. I also use Mathematica (Home Edition) to compare. However as
Mathematica is largely symbolic, I prefer Python.

 

However I recently talked to a guy online and he told me the following,
which actually intrigued and surprised me:

 

The vast majority of numerical codes in science, including positional
astronomy, are written in Fortran and C/C++.  If you wish to use these codes
in minority and less efficient languages such as Python and VBA, learning to
translate this code into those languages is a skill you will have to
acquire.

 

The codes in question are referring to a query I posed to him regarding
the GUST86 theory on the computational position of Uranus' natural
satellites authored by Laskar and Jacobson in 1987. The code is readily
downloadable in Fortran at the IMCCE ftp site.

 

But his statement is insinuating that Python is inferior to Fortran as a
mathematical tool and that all of the scientific community prefers to use
Fortran.

 

My question is simple: Is he right or wrong?

 

Thanks

Vick

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Re: [Tutor] Hi

[William Ray Wing]

 On Apr 11, 2015, at 8:32 AM, Vick vick1...@orange.mu wrote:
 

[byte]

 However I recently talked to a guy online and he told me the following,
 which actually intrigued and surprised me:
 
 The vast majority of numerical codes in science, including positional
 astronomy, are written in Fortran and C/C++.  If you wish to use these codes
 in minority and less efficient languages such as Python and VBA, learning to
 translate this code into those languages is a skill you will have to
 acquire.
 
 The codes in question are referring to a query I posed to him regarding
 the GUST86 theory on the computational position of Uranus' natural
 satellites authored by Laskar and Jacobson in 1987. The code is readily
 downloadable in Fortran at the IMCCE ftp site.
 
 But his statement is insinuating that Python is inferior to Fortran as a
 mathematical tool and that all of the scientific community prefers to use
 Fortran.
 
 My question is simple: Is he right or wrong?
 
 

He is probably right, but only because most large scientific codes have 
historical roots that date back to the days when FORTRAN was the only language 
readily available on the computers scientists used.  Even today, FORTRAN 
compilers can frequently optimize typical scientific code to tighter (faster) 
executable code than the compilers for other, more modern, richer languages.  
HOWEVER, that said, more and more scientific code is being written with Python 
as the organizing language which calls mathematical libraries written in 
FORTRAN.  Libraries like numpy make heavy use of FORTRAN arrays, while allowing 
the scientific programmer to concentrate on the higher levels of the science 
being modeled.

Bill

 
 Thanks
 
 Vick
 
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Re: [Tutor] Hi

[Vick]

Hi,

Thanks for replying!

I understand as you said that since it was the very first language available
to them therefore scientists at large got stuck with it as I presume it
would have become the primary programming language example given in their
textbooks or study materials.

However your reply does not answer the first part of the proposition of my
question!

Given that all scientists like to code in Fortran but does it mean that
Python is inferior to it in terms of mathematical / scientific computation?

Thanks
Vick



-Original Message-
From: William Ray Wing [mailto:w...@mac.com] 
Sent: Saturday, 11 April, 2015 17:40
To: Vick
Cc: William R. Wing; webmas...@python.org; tutor@python.org
Subject: Re: [Tutor] Hi


 On Apr 11, 2015, at 8:32 AM, Vick vick1...@orange.mu wrote:
 

[byte]

 However I recently talked to a guy online and he told me the 
 following, which actually intrigued and surprised me:
 
 The vast majority of numerical codes in science, including positional 
 astronomy, are written in Fortran and C/C++.  If you wish to use these 
 codes in minority and less efficient languages such as Python and VBA, 
 learning to translate this code into those languages is a skill you 
 will have to acquire.
 
 The codes in question are referring to a query I posed to him 
 regarding the GUST86 theory on the computational position of Uranus' 
 natural satellites authored by Laskar and Jacobson in 1987. The code 
 is readily downloadable in Fortran at the IMCCE ftp site.
 
 But his statement is insinuating that Python is inferior to Fortran as 
 a mathematical tool and that all of the scientific community prefers 
 to use Fortran.
 
 My question is simple: Is he right or wrong?
 
 

He is probably right, but only because most large scientific codes have
historical roots that date back to the days when FORTRAN was the only
language readily available on the computers scientists used.  Even today,
FORTRAN compilers can frequently optimize typical scientific code to tighter
(faster) executable code than the compilers for other, more modern, richer
languages.  HOWEVER, that said, more and more scientific code is being
written with Python as the organizing language which calls mathematical
libraries written in FORTRAN.  Libraries like numpy make heavy use of
FORTRAN arrays, while allowing the scientific programmer to concentrate on
the higher levels of the science being modeled.

Bill

 
 Thanks
 
 Vick
 
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Re: [Tutor] Hi

[Steven D'Aprano]

On Sat, Apr 11, 2015 at 08:35:08PM +0400, Vick wrote:

 Given that all scientists like to code in Fortran but does it mean that
 Python is inferior to it in terms of mathematical / scientific computation?

Scientists do not like to code in Fortran. Anybody who tells you that is 
mistaken. If they wanted to be programmers, they would have become 
programmers, not scientists. If they *have* to program, they will, but 
they would rather do science, not programming.

No, Python is not inferior. It is just different. It is designed to have 
different strengths and weaknesses compared to Fortran.

Strengths of Fortran:

- You can write very fast, powerful numeric programs.
- Fortran excels at high-speed number-crunching.
- Fortran is an old language, in fact it is the first (and therefore 
  oldest) programming language. Because it has been around since the 
  1950s, there are lots of Fortran libraries you can use -- if you can 
  find them, or afford them.

Weaknesses of Fortran:

- It is difficult to write Fortran code.
- It is an old language which lacks modern programming features.
- It is hard to work with strings or do anything except 
  number-crunching.
- It is a very low-level language, which means you have to care about 
  things that have nothing to do with the problem you are trying to 
  solve, like memory.


Strengths of Python:

- It is a modern language with many modern features that Fortran lacks.
- It is easy to work with strings and other associated data structures.
- It is a high-level language that automatically looks after all the 
  boring book-keeping details, like memory.
- It excels at rapid application development.
- It excels at being a glue-language for calling pre-written C or 
  Fortran libraries.

Weaknesses:

- Pure Python code may be a bit slower that C or Fortran code. (But that 
  doesn't matter, if you can call a C or Fortran library to do the heavy 
  lifting, and leave Python to do the parts that C or Fortran struggle 
  with.)


When people tell you that real scientists write their code in Fortran, 
they are being macho pretentious fools. Do real scientists also make 
their own test tubes from sand they dug out of the ground themselves? 
No, of course not. It isn't 1800 any more, and the average scientist no 
more needs to program in Fortran than they need to grind their own 
lenses. Some scientists may still need to use Fortran, but that is a 
sign that they are still stuck with using ancient computer programs, not 
a good thing to be copied.

To give an analogy, Fortran is like flying a Suyez rocket. It is very 
difficult to learn to fly, but once you master it you can go into space 
in seconds. But it will takes years of training and months of 
preparation for each flight.

Python is like driving a car: it won't get you into space, but it takes 
weeks to learn to drive a car, not years, and you can jump in the car 
and drive to the shops with no preparation needed.

And you can get in your car and drive to the Suyez rocket, but you 
cannot get in the Suyez and fly to where you parked your car.

Which is better? Well, it depends. If you want to drive to the shops, 
the Suyez is completely useless. It costs fifty million dollars every 
time you use it, and you cannot even get to the shops.

If you want to spend six months writing a Fortran program to analysis 
your data, you can, and when you have finished, it will run in five 
seconds. Or you can spend six days writing it in Python, and it will run 
in five minutes. Which is better?

To be more precise: Python can use Fortran and C libraries to do the 
heavy lifting, the difficult work. Doing that from Fortran or C is a 
horrible experience: they are hard languages to learn, and hard to use. 
But using those libraries from Python is fast, and fun, and easy, and 
that means that scientists can spend more time doing science and less 
time trying to program the computer.



-- 
Steve
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Re: [Tutor] Hi

[Alan Gauld]

On 11/04/15 13:32, Vick wrote:


The vast majority of numerical codes in science, including positional
astronomy, are written in Fortran and C/C++.


True, because the vast majorioty of scientific codes (ie libraries) 
were written many years ago and are still maintained in the languages 
used back then. Mainly that was Fortran for science.


The vast majpority of *new* scientific code being written is not in 
Fortran (and not much in C either). In fact I don't know of any local 
university that still teaches Fortran as part of their normal

science or math syllabus.

Most new scientific work is done in Mathematica or similar high
level language and then translated when needed into a lower
level language like C or increasingly Java. (And if its
statistics often into R.)


If you wish to use these codes in minority and less efficient

 languages such as Python and VBA,

Minority - False. There are certainly more VBA programmers
than Fortan ones. And probably as many as there are C/C++
Python is only a little way behind Fortan if at all.
But if we limit ourselves to the scientific community
then its closer to being true.


 learning to translatethis code into those languages

 is a skill you will have to acquire.

Completely false. Almost all modern scripting languages
have mechanisms to call C libraries easily. (And high
quality  Fortran to C translators exist.)

Only if you need to write very high performance routines
that do not already exist - ie you are a research
scientist or mathematician - do you need to learn C
or Fortran. And even then its unlikely to be your
first choice.


The codes in question are referring to a query I posed to him regarding
the GUST86 theory on the computational position of Uranus' natural
satellites authored by Laskar and Jacobson in 1987. The code is readily
downloadable in Fortran at the IMCCE ftp site.


Have you investigated the SciPy libraries, and especially
the SciKit collection of specialist libraries. There
are several astro libraries in there.
Most are written in C but wrapped for use from Python.


But his statement is insinuating that Python is inferior to Fortran as a
mathematical tool


No, he quite correctly states that Python is less efficient
than C or Fortran for numerical analysis. That is true of
mainstream, Python. There are various projects attempting
to address that shortfall. But there are many dimensions
to the goodness of a programming language and efficiency
(ie runtime speed)  is only one of them. And on modern
computing hardware it is rarely the most important one.
Others include development speed (programming efficiency),
portability, reliability, connectivity, abstraction capability,
readability/maintainability, tool support etc.

To say any language is inferior to another needs to
be qualified by the dimension(s) being measured.
I see Steven has just posted a similar mail that goes
into the comparisons in more detail. So I'll stop
here :-)


and that all of the scientific community prefers to use
Fortran.


That depends who you talk to. I know many scientists who
swear by Mathematica and Matlab and don't use anything else.


My question is simple: Is he right or wrong?


The answer is less simple: it depends...

Finally, for a more light-hearted take on the topic, see:

http://www.ee.ryerson.ca/~elf/hack/realmen.html

For maximum offence substitute Python for Pascal ;-)

--
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] Hi

[Steven D'Aprano]

Hi Vick, and welcome!

My replies to your questions are below, interleaved with your comments.

On Sat, Apr 11, 2015 at 04:32:38PM +0400, Vick wrote:

 However I recently talked to a guy online and he told me the following,
 which actually intrigued and surprised me:
 
 The vast majority of numerical codes in science, including positional
 astronomy, are written in Fortran and C/C++.  If you wish to use these codes
 in minority and less efficient languages such as Python and VBA, learning to
 translate this code into those languages is a skill you will have to
 acquire.
[...]
 But his statement is insinuating that Python is inferior to Fortran as a
 mathematical tool and that all of the scientific community prefers to use
 Fortran.

 My question is simple: Is he right or wrong?

He is partly right, partly wrong. But mostly wrong. Twenty years ago, if 
you wanted to do scientific computing, C and Fortran were essential. 
They are still very important, but they are no longer essential.

There are many professional-quality mathematical libraries. Older 
libraries are nearly all written in C/C++ or Fortran. Some are older 
libraries are written in Pascal, but because few people use Pascal any 
more, you won't find many of them still in use. Some newer libraries are 
written in Java. In the future, I would expect new scientific libraries 
to start coming out written in Julia:

http://julialang.org/

Although these libraries are written in C or Fortran, you don't need to 
program in those two languages to *use* those libraries. Most scripting 
languages like Python, Lua or Ruby include ways to call code in C or 
Fortran libraries as if they were written in Python (or Lua, Ruby, and 
so forth). We call languages like Python a glue language, because it 
is very good for gluing together code from different libraries. You 
want to use this library for planetary orbit calculations, written in 
Fortran, and that library for calculating lunar eclipses written in C, 
so you use a Python script to bring them together.

Many mathematicians, statisticians and scientists use products such as 
Mathematica, Matlab, R, SAS, Minitab, Maple, and similar. These are all 
good products that have been around for a long time, with their own 
strengths and weaknesses.

One Python-based product which is becoming widely used in scientific 
circles is Numpy, together with its sister-library Scipy. The core 
numeric routines in Numpy and Scipy are mostly written in C and Fortran, 
but the interface is designed for use with Python.

http://www.numpy.org/
http://www.scipy.org/

Another Python product is SAGE, which aims to be a free alternative to 
Maple, Mathematica and other similar products.

http://www.sagemath.org/

The idea is to create a group of powerful maths, statistics and 
scientific libraries. Those libraries can use whatever language they 
want, and often they are written in C and Fortran, but the glue that 
holds them together is Python. Together, they combine the power of 
low-level, hard-to-use but powerful fast languages like Fortran and C 
with the ease of use and convenience of modern high-level languages like 
Python.

The core of scientific computing with Python includes:

Numpy - fast N-dimensional array calculations
Scipy - scientific computing libraries
Matplotlib - 2D graphing
IPython - enhanced interactive console with Mathematica-like notebook
Sympy - symbolic mathematics 
Pandas - data analysis
SAGE - integrated scientific computing system

Parts of these are written in Python, and parts in C, Fortran, 
Javascript, and potentially any language imaginable.

I also expect that people can start using PyPy to run pure-Python code 
almost as fast as C:

http://pypy.org/

Or they can use Cython to write C code using Python syntax:

http://cython.org/
‎
All of these are parts of the Python ecosystem, and are why Python is 
currently becoming the go-to language for scientific computing. Where 
scientists used to write code in Fortran (hard and slow to write, but 
fast to run) or expensive proprietary products like Mathematica or 
Matlab, many people are gradually moving towards the Python ecosystem of 
Python, Numpy, IPython notebooks, and others.

This post explains Python's advantages over Matlab, why the author 
thinks that scientific computing will continue to move towards Python, 
and links to a number of other good articles from people who already 
have done so.

http://cyrille.rossant.net/why-using-python-for-scientific-computing/


My advice if you want to be a good scientific programmer:

- Stay with Python. Anyone who tries to tell you that you need to know 
  how to program in Fortran or C to do scientific computing is wrong.
- Learn how to program in Python as well as possible.
- Learn when *not* to program in Python, and know when to use existing 
  tools already written in C, Fortran or other languages. Chances are
  very good that Numpy, Scipy and others above already solve some of 
  your problems.
- If 

Re: [Tutor] Hi

[Martin A. Brown]

Greetings Steven,

Much great advice snipped.

Is it possible (using U+1F600 through U+1F64F or otherwise) to offer 
a standing ovation for such a relevant, thorough, competent and 
well-written reply?


Thank you, as always,

-Martin

(You know, Steven, we had gotten so accustomed to your slapdash 
answers, that this one comes as a huge surprise.)


--
Martin A. Brown
http://linux-ip.net/
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[Tutor] Hi!

[Vlad Olariu]

Hello. I am new to python and mailing lists. Where should I post some code
if I need to?
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Re: [Tutor] Hi!

[Mark Lawrence]

On 09/11/2013 21:04, Vlad Olariu wrote:

Hello. I am new to python and mailing lists. Where should I post some
code if I need to?



Here but only after you've read this http://sscce.org/

--
Python is the second best programming language in the world.
But the best has yet to be invented.  Christian Tismer

Mark Lawrence

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Re: [Tutor] Hi!

[Joel Goldstick]

On Sat, Nov 9, 2013 at 4:04 PM, Vlad Olariu florinvlad.ola...@gmail.com wrote:
 Hello. I am new to python and mailing lists. Where should I post some code
 if I need to?

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Tell us your python version and OS version

Try to create a small code example that shows the question you have.

If you get an error in your code, copy and paste the complete traceback here

Some people post to pastebin, but many others don't like that.  So,
best to keep example small and post here

Finally, post in plaintext, not html


-- 
Joel Goldstick
http://joelgoldstick.com
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Re: [Tutor] Hi!

[Amit Saha]

Hello,

On Sun, Nov 10, 2013 at 7:04 AM, Vlad Olariu
florinvlad.ola...@gmail.com wrote:
 Hello. I am new to python and mailing lists. Where should I post some code
 if I need to?

Welcome. Here is an example of a post with code. Assume that I am
explaining to someone how they can exit out a while loop before the
condition violated the first time:

A while loop is an example of an entry controlled loop. This means
that the condition is checked before entering the loop. Hence, this
means if your loop condition was violated during the previous
iteration, but not at the beginning, your loop will terminate after
the first violation, not before it.

Here is a simple example:

 a = 1
 while a  5:
... a = a+3
... print a
...
4
7



.. and so on. Also switch to Plain Text in your Gmail window before
you post. (if you do not know what this means, please search on the
Web a bit).

Good Luck.

Best.
Amit.


-- 
http://echorand.me
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Re: [Tutor] hi

[Oscar Benjamin]

On 20 August 2013 13:49, Vick vick1...@orange.mu wrote:

 From: Oscar Benjamin [mailto:oscar.j.benja...@gmail.com]

 Well just send me some tutorial on how to build and obtain the
 coefficients for the butcher tableau for the RK4 as an example, and
 after I've mastered it, I'd give the dopri8 a shot.

 I am up for it so I'll see if I can find time to write a script that shows
 how to do it.

 [Vick] Hope you've had the time to code it. I'm waiting for it.

Sorry, I haven't found the time yet. It is still on my todo list though!

 By the way your code for the Adams-Moulton coefficients are actually the
 Adams-Bashforth ones and so I copied it and modified the copy to have the
 Adams-Moulton coefficients as well. This means that I have now an nth-order
 predictor-corrector method to solve for ODEs.

Oh sorry. That'll be a cut and paste error. My code lives in a private
software library that I keep meaning to release on PyPI but it's not
ready for public consumption in quite a number of ways.

I'm glad that you worked it out though. You''ll probably understand
what I mean now when I say that the AM or AB integrators need a
secondary algorithm to bootstrap. The accuracy of the subsequent AM/AB
method depends on the accuracy of that step. In the worst case you can
just use rk4 with a very small time-step for this bit though.


Oscar
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Re: [Tutor] hi

[Vick]

-Original Message-
From: Oscar Benjamin [mailto:oscar.j.benja...@gmail.com] 
Sent: Tuesday, 13 August, 2013 01:01


 Well just send me some tutorial on how to build and obtain the 
 coefficients for the butcher tableau for the RK4 as an example, and 
 after I've mastered it, I'd give the dopri8 a shot.

I am up for it so I'll see if I can find time to write a script that shows
how to do it.

[Vick] Hope you've had the time to code it. I'm waiting for it.

By the way your code for the Adams-Moulton coefficients are actually the
Adams-Bashforth ones and so I copied it and modified the copy to have the
Adams-Moulton coefficients as well. This means that I have now an nth-order
predictor-corrector method to solve for ODEs.

Vick

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Re: [Tutor] hi

[Vick]

Hi,

It just plot one line. How to print several lines?

I've attached your example and I've corrected my own 3d code which works now
but it is not an animation. So how can I plot it using the code you gave me?

By the way, I think you know that I'm trying to plot for n-body problem?
Have you made a python code for the n-body problem? Mine works, but I'm just
having trouble with 3d plotting of the orbits. And also I have searched the
web on how to integrate conservation of energy as you suggested to me, but I
couldn't find any article that talks about 1st order ODEs for energy, and
the annotation is different from mine.

PS: Also how do you make the plot run only once without having to do it over
and over again?

Thanks
Vick

-Original Message-
From: Oscar Benjamin [mailto:oscar.j.benja...@gmail.com] 
Sent: Tuesday, 06 August, 2013 18:40
To: Vick
Cc: tutor@python.org
Subject: Re: [Tutor] hi

On 1 August 2013 12:32, Vick vick1...@orange.mu wrote:
 Hi,

Hi Vick, sorry I've been away and I've only had a chance to look at this
now.

 As per your request below, I have attached a stand-alone example 
 (test3d.py) of my problem. I am trying to plot in 3D using ion() from a
loop.

Basically don't use ion() for animation: it is intended for interactive use.
Use matplotlib's animation API for animation. See
here:
http://jakevdp.github.io/blog/2012/08/18/matplotlib-animation-tutorial/

I've put example scripts below. Both run fine on this computer. You'll want
a recent matplotlib version.

Here's a 2d animation script:

#!/usr/bin/env python
# 2d animation

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation

fig = plt.figure(figsize=(5, 5))
ax = fig.add_axes([0.15, 0.15, 0.70, 0.70]) line, = ax.plot([], [],
linewidth=2)

def init():
ax.set_xlim([-1, 1])
ax.set_ylim([-1, 1])
line.set_data([], [])
return line,

def animate(i):
t = dt * np.arange(i)
x = np.cos(omega * t)
y = np.sin(omega * t)
line.set_data(x, y)
return line,

dt = .02 # in seconds
T = 10   # Period (seconds)
omega = 2 * np.pi / T  # 0.1 Hz

anim = animation.FuncAnimation(fig, animate, init_func=init,
   frames=int(T/dt), interval=int(1000*dt),
blit=True)

plt.show()


And here's a 3d script:

#!/usr/bin/env python
# 3d animation

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
from mpl_toolkits.mplot3d import Axes3D

fig = plt.figure(figsize=(5, 5))
ax = fig.add_axes([0.15, 0.15, 0.70, 0.70], projection='3d') line, =
ax.plot([], [], [], linewidth=2)

def init():
ax.set_xlim([-1, 1])
ax.set_ylim([-1, 1])
ax.set_zlim([0, 10])
line.set_data([], [])
return line,

def animate(i):
t = dt * np.arange(i)
x = np.cos(omega * t)
y = np.sin(omega * t)
z = t
line.set_data(x, y)
line.set_3d_properties(z)  # WTF!
return line,

dt = .02 # in seconds
T = 10   # Duration (seconds)
omega = 2 * np.pi  # 1 Hz

anim = animation.FuncAnimation(fig, animate, init_func=init,
   frames=int(T/dt), interval=int(1000*dt),
blit=True)

plt.show()




Oscar
from pylab import *
#import pylab
from mpl_toolkits.mplot3d.axes3d import Axes3D
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import axes3d


def drange(start, stop, step):
r = start
while r  stop:
yield r
r += step


a=[]
b=[]
z1=[]
c=[]
d=[]
z2=[]




#plt.ion()

fig = plt.figure(dpi=100)
ax = axes3d.Axes3D(fig)#fig.add_subplot(111, projection = '3d')

t = 0
dt = 1
tn= 50

for i in drange (t+dt, tn,dt):
aa = sin(i)
bb = cos(i)
cc = aa*bb
aa1 = 1.5 *sin(i)
bb1 = 1.5*cos(i)
cc1 = aa1*bb1
a.append(aa)
b.append(bb)
z1.append(cc)
c.append(aa1)
d.append(bb1)
z2.append(cc1)
#clf()
#ax.plot(a,b,z1, marker='o', linestyle='None')
#ax.plot(c,d,z2, marker='o', linestyle='None')
ax.plot(a,b,z1)
ax.plot(c,d,z2)
plt.show()

#!/usr/bin/env python
# 2d animation

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation

fig = plt.figure(figsize=(5, 5))
ax = fig.add_axes([0.15, 0.15, 0.70, 0.70])
line, = ax.plot([], [], linewidth=2)

def init():
ax.set_xlim([-1, 1])
ax.set_ylim([-1, 1])
line.set_data([], [])
return line,

def animate(i):
t = dt * np.arange(i)
x = np.cos(omega * t)
y = np.sin(omega * t)
line.set_data(x, y)
return line,

dt = .02 # in seconds
T = 10   # Period (seconds)
omega = 2 * np.pi / T  # 0.1 Hz

anim = animation.FuncAnimation(fig, animate, init_func=init,
   frames=int(T/dt), interval=int(1000*dt), 
blit=True)

plt.show()




#!/usr/bin/env python
# 3d animation

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
from mpl_toolkits.mplot3d import Axes3D

fig = plt.figure(figsize=(5, 5))
ax = fig.add_axes([0.15, 0.15, 0.70, 0.70], projection='3d')
line, = ax.plot

Re: [Tutor] hi

[Vick]

Hi,

As per your request below, I have attached a stand-alone example (test3d.py)
of my problem. I am trying to plot in 3D using ion() from a loop.

The code should plot x,y,z coordinates from a loop in ion(). We should see
the plot line moving and the marker moving as well.

I have also attached a working 2d-plot (test2d.py) to show what it's
supposed to do. The 3d plot (test3d.py) should plot the same but with an
additional z coordinates and a z axis!

Thanks
Vick

-Original Message-
From: Oscar Benjamin [mailto:oscar.j.benja...@gmail.com] 
Sent: Thursday, 01 August, 2013 01:42
To: Vick
Subject: Re: [Tutor] hi

On 31 July 2013 22:20, Vick vick1...@orange.mu wrote:
 Hello,

Hi Vick,

I would prefer it if you would send questions like this to the tutor mailing
list rather than directly to me. This is because:
1) I'm often unable to respond and there are many other people there who
could help (I may be the only one there who understands ODEs but I'm
certainly not the only one who understands matplotlib).
2) It's helpful for others on the tutor mailing list to see the kind of
problems (and solutions) that people new to Python are working with.
3) Any problem/solution gets publicly archived for future reference.

 Can you help me please with plotting in 3D using ion()?

 My code is the following:

 from pylab import *
 #import pylab
 from mpl_toolkits.mplot3d.axes3d import Axes3D import 
 matplotlib.pyplot as plt from mpl_toolkits.mplot3d import axes3d

 plt.ion()

 fig = plt.figure(dpi=100)
 ax = axes3d.Axes3D(fig)#fig.add_subplot(111, projection = '3d')


 tn= mpf('300')#mpf('800')*dt

 for i in drange (t+dt, tn,dt):
 mi = testran(i,mi,dt)
 #print i+ dt,   , mi
 a.append(mi[0])
 b.append(mi[1])
 z1.append(mi[2])
 c.append(mi[6])
 d.append(mi[7])
 z2.append(mi[8])
 #clf()
 ax.plot(a,b,z1)#linestyle='None', marker='o', markersize = 5)
 ax.plot(a,b,z1, marker='o', linestyle='None')
 ax.plot(c,d,z2)
 ax.plot(c,d,z2, marker='o', linestyle='None')
 #draw()

 #grid()
 #show()

 I'm trying to plot in 3D, coordinates that are appended from a loop 
 using ion(), but it doesn't plot.

I get something different:

$ python plot3d.py
Traceback (most recent call last):
  File plot3d.py, line 13, in module
tn= mpf('300')#mpf('800')*dt
NameError: name 'mpf' is not defined

Where does the mpf function come from? There are many other symbols that are
not defined (t, dt, testran, ...) so presumably this code is incomplete
somehow.

Could you please make a complete example illustrating the problem you have
and then post it to the tutor list?


Oscar
from pylab import *

import matplotlib.pyplot as plt



def drange(start, stop, step):
r = start
while r  stop:
yield r
r += step


a=[]
b=[]
z1=[]
c=[]
d=[]
z2=[]




plt.ion()

fig = plt.figure(dpi=100)
ax = fig.add_subplot(111)

t = 0
dt = 1
tn= 50

for i in drange (t+dt, tn,dt):
aa = sin(i)
bb = cos(i)
aa1 = 1.5 *sin(i)
bb1 = 1.5*cos(i)
a.append(aa)
b.append(bb)
c.append(aa1)
d.append(bb1)
clf()
plot(a,b)#linestyle='None', marker='o', markersize = 5)
plot(aa,bb, marker='o', linestyle='None')
plot(c,d)
plot(aa1,bb1, marker='o', linestyle='None')
draw()

#grid()
#show()
from pylab import *
#import pylab
from mpl_toolkits.mplot3d.axes3d import Axes3D
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import axes3d


def drange(start, stop, step):
r = start
while r  stop:
yield r
r += step


a=[]
b=[]
z1=[]
c=[]
d=[]
z2=[]




plt.ion()

fig = plt.figure(dpi=100)
ax = axes3d.Axes3D(fig)#fig.add_subplot(111, projection = '3d')

t = 0
dt = 1
tn= 50

for i in drange (t+dt, tn,dt):
aa = sin(i)
bb = cos(i)
cc = aa*bb
aa1 = 1.5 *sin(i)
bb1 = 1.5*cos(i)
cc1 = aa1*bb1
a.append(aa)
b.append(bb)
z1.append(cc)
c.append(aa1)
d.append(bb1)
z2.append(cc1)
#clf()
ax.plot(a,b,z1)#linestyle='None', marker='o', markersize = 5)
ax.plot(a,b,z1, marker='o', linestyle='None')
ax.plot(c,d,z2)
ax.plot(c,d,z2, marker='o', linestyle='None')
plt.draw()

#grid()
#show()
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Re: [Tutor] hi

[Vick]

Hello,

 

Thanks for taking the time to reply!

 

However, I had already solved the problem a few days ago on my own.

 

The DOPRI 8(7)13 is the Dormand Prince 8th order with 13 stages method for
solving  http://en.wikipedia.org/wiki/Ordinary_differential_equations
ordinary differential equations. It is a member of the Runge-Kutta family of
ODE solvers. I have been able to reproduce it in Python with a
multi-variable capability. On a particular test equation the error of the
RK4 is about 1e-4 whereas the DOPRI 8(7)13 is about 1e-13.

 

I have then used the multi-variable DOPRI to compute for the n-body problem
using 1st order ODEs which requires you to have 4 equations for 1 planet. I
have already made a 10-body problem through an n-body solver in python and
using DOPRI as my integrator.

 

It works fine.

 

Thanks again for your time and consideration.

 

Regards

Vick

 

 

-Original Message-
From: Oscar Benjamin [mailto:oscar.j.benja...@gmail.com] 
Sent: Monday, 22 July, 2013 15:59
To: Vick
Cc: Tutor@python.org
Subject: Re: [Tutor] hi

 

On 12 July 2013 11:08, Vick  mailto:vick1...@orange.mu
vick1...@orange.mu wrote:

 Hi,

 

Hi Vick,

 

Sorry for the delayed response I didn't see this email until a while after
you sent it.

 

 I have written a code to perform a numerical solution to 1st order 

 Ordinary Differential Equations (ODEs). I have written codes for the 

 famous Runge Kutta 4th order and the DOPRI 8(7)13. However the codes 

 are for 1 variable only; viz. the y variable.

 

It would be good to show us the code for this in your email (not in an
attachment). Also the code should be complete: the code uses a function
rungkdp8 which is not shown. Where did that come from? Until you know what
you're doing you should test your integrator on a simpler set of equations.
Also when posting to a mailing list you should simplify the problem as much
as possible which would mean using simpler ODEs. In short read this:

 http://sscce.org/ http://sscce.org/

 

The code attached is incorrect as it applies each stage of the Runge-Kutta
method to all time-steps sequentially before moving on to the next stage. It
should apply each stage for one time step and then use the output of that
for the next time-step. In other words you need to change the order of the
loops.

 

Here is an example of how to implement an Euler stepper that should
hopefully get you started on the right track. I've deliberately avoided
using numpy in this example even though it makes most of this easier. I did
this to focus on the basics of Python which you should learn first.

 

# integrator.py

 

nan = float('nan')

 

# indices for the two variables in the system POS = 0 VEL = 1 VARS = ['pos',
'vel']

 

# system has one parameter OMEGA

OMEGA = 10  # Frequency in Hz is OMEGA / 2pi

 

# function for the derivative of the system def shm(t, x, dxdt):

'''Equation of motion for a mass in a spring with freq OMEGA'''

dxdt[POS] = x[VEL] # Python uses square brackets for indexing

dxdt[VEL] = - OMEGA**2 * x[POS]

 

# Initial conditions for the problem

x0 = [nan] * 2

x0[POS] = 1

x0[VEL] = 0

 

# This is the function that you should replace with e.g. rk4 or dopri8 def
euler(t1, x1, t2):

'''Take 1 Euler step from x1 at t1 to x2 at t2'''

# Create empty lists for answer

x2 = [nan] * len(x1)

dxdt = [nan] * len(x1)

# Call derivative function to fill in dxdt

shm(t1, x1, dxdt)

# Compute x2 and return

dt = t2 - t1

for n in range(len(x1)):

x2[n] = x1[n] + dt * dxdt[n]

return x2

 

def solve(ts, x0):

'''Compute states corresponding to the times in ts

 

x0 is the state at ts[0] (the initial condition).

'''

# Create an empty list of lists for the solution

Xt = [x0[:]]  # The initial conditions

# Loop through timesteps computing the next value

for n in range(len(ts) - 1):

Xt.append(euler(ts[n], Xt[n], ts[n+1]))

return Xt

 

def print_line(*items):

print(', '.join(str(i) for i in items))

 

def print_solution(ts, Xt, vars):

print_line('t', *vars)

for t, x in zip(times, Xt):

print_line(t, *x)

 

# Numerical parameters for the solution

DT = 0.001

t0 = 0

T  = 1

times = [t0]

while times[-1]  T:

times.append(times[-1] + DT)

 

# Solve and print

Xt = solve(times, x0)

print_solution(times, Xt, VARS)

 

 

 I have written another code in Excel VBA for DOPRI 8 for a 

 multi-variable capability. However I have not been able to reproduce 

 it in Python. I'm having trouble in making arrays or lists, I don't 

 know which is supposed to work.

 

 I have attached my Excel VBA code for a multi-variable numerical 

 integrator in PDF format. This does work in Excel. I have also attached my
python code.

 

I'm not familiar with Excel VBA but I think that this code suffers from the
same problem that the loop over stages takes place outside the loop over
time-steps so I believe

Re: [Tutor] hi

[Joel Goldstick]

On Fri, Jul 12, 2013 at 6:08 AM, Vick vick1...@orange.mu wrote:

 Hi,

 ** **

 I’m using Windows 7 and Python 2.7.3

 ** **

 I have written a code to perform a numerical solution to 1st order
 Ordinary Differential Equations (ODEs). I have written codes for the famous
 Runge Kutta 4th order and the DOPRI 8(7)13. However the codes are for 1
 variable only; viz. the “y” variable.

 ** **

 I have written another code in Excel VBA for DOPRI 8 for a multi-variable
 capability. However I have not been able to reproduce it in Python. I’m
 having trouble in making arrays or lists, I don’t know which is supposed to
 work.

 ** **

 I have attached my Excel VBA code for a multi-variable numerical
 integrator in PDF format. This does work in Excel. I have also attached my
 python code.

 ** **

 Can anyone help me out please?


So are you saying your python code doesn't run, or it runs but doesn't give
the same answers as your vb code? If your python code throws an exception
you should list the traceback for better help.
Also, try using a better subject line next time.

 

 Thanks

 Vick

 ** **

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-- 
Joel Goldstick
http://joelgoldstick.com
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[Tutor] Hi, First question

[Patrick Williams]

Hi so I am making a bit of code to extract a bit of numbers data from a
file and then find the average of that data, however while I can get the
code to extract each specific piece of data I need, I can't seem to get the
numbers to add separately  so I can get a proper average. My sum1 variable
seems to only take the last bit of data entered. I was just wondering if
anyone knows what I'm doing wrong, the course I'm following hadn't started
using regex (or even proper lists) at this point, so there must be a way to
do it without. here's the code. the average of the data should be 0.6789 or
something, but I get 0.0334343 or something.

count=0
lst=list()
fname='mbox-short.txt'
fhand=open(fname)
for line in fhand:
if line.startswith('X-DSPAM-Confidence:'):
count=count+1
colpos=line.find(':')
zpos=line.find('0',colpos)
num=float(line[zpos:50])
sum1=0+num
avg=float(sum1)/int(count)
print 'Count-', count,'--', 'Average-', avg

Any help at all is appreciated, and thanks in advance.
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Re: [Tutor] Hi, First question

[Alexander]

On Sat, Jun 15, 2013 at 1:22 AM, Patrick Williams pdw0...@gmail.com wrote:

 Hi so I am making a bit of code to extract a bit of numbers data from a
 file and then find the average of that data, however while I can get the
 code to extract each specific piece of data I need, I can't seem to get the
 numbers to add separately  so I can get a proper average. My sum1 variable
 seems to only take the last bit of data entered. I was just wondering if
 anyone knows what I'm doing wrong, the course I'm following hadn't started
 using regex (or even proper lists) at this point, so there must be a way to
 do it without. here's the code. the average of the data should be 0.6789 or
 something, but I get 0.0334343 or something.

 count=0
 lst=list()
 fname='mbox-short.txt'
 fhand=open(fname)
 for line in fhand:
 if line.startswith('X-DSPAM-Confidence:'):
 count=count+1
 colpos=line.find(':')
 zpos=line.find('0',colpos)
 num=float(line[zpos:50])
 sum1=0+num
 avg=float(sum1)/int(count)
 print 'Count-', count,'--', 'Average-', avg

 Any help at all is appreciated, and thanks in advance.

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Please include the mbox-short.txt file. Also you should include the
output of your code (copy and paste it).


-- 
Alexander
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Re: [Tutor] Hi, First question

[Chris “Kwpolska” Warrick]

On Sat, Jun 15, 2013 at 7:22 AM, Patrick Williams pdw0...@gmail.com wrote:
 Hi so I am making a bit of code to extract a bit of numbers data from a file
 and then find the average of that data, however while I can get the code to
 extract each specific piece of data I need, I can't seem to get the numbers
 to add separately  so I can get a proper average. My sum1 variable seems to
 only take the last bit of data entered. I was just wondering if anyone knows
 what I'm doing wrong, the course I'm following hadn't started using regex
 (or even proper lists) at this point, so there must be a way to do it
 without. here's the code. the average of the data should be 0.6789 or
 something, but I get 0.0334343 or something.

 count=0
 lst=list()

`lst = []` is the preferred syntax.

 fname='mbox-short.txt'
 fhand=open(fname)
 for line in fhand:
 if line.startswith('X-DSPAM-Confidence:'):
 count=count+1
 colpos=line.find(':')
 zpos=line.find('0',colpos)
 num=float(line[zpos:50])
 sum1=0+num
 avg=float(sum1)/int(count)
 print 'Count-', count,'--', 'Average-', avg

 Any help at all is appreciated, and thanks in advance.

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I don’t know what file you used, but the message you sent got this
header from Gmail, and the format doesn’t seem to be much different:

 X-Spam-Evidence: '*H*': 0.79; '*S*': 0.00; 'separately': 0.09;
'wrong,': 0.09; 'subject:question': 0.10; 'code.': 0.18;
'variable': 0.18; 'bit': 0.19; 'advance.': 0.19; 'seems': 0.21;
'8bit%:5': 0.22; 'print': 0.22; 'skip:l 30': 0.24; '\xa0so': 0.24;
 [snip 11 more lines]
(replaced tabstops with spaces)

Can you guess what’s wrong in your code?

You are reading only the first line.  There are more.  How do you
handle that?  You need to make your algorithm read all the further
lines that begin with the indentation your thing uses (it might be the
tab character '\t' or some spaces), and stop when it encounters
another header.  This can be done either by checking if the line
begins with the indentation OR by checking match with regexp
'[A-Za-z]+: .+'

--
Kwpolska http://kwpolska.tk | GPG KEY: 5EAAEA16
stop html mail| always bottom-post
http://asciiribbon.org| http://caliburn.nl/topposting.html
   
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Re: [Tutor] Hi, First question

[Mark Lawrence]

On 16/06/2013 16:55, Chris “Kwpolska” Warrick wrote:

On Sat, Jun 15, 2013 at 7:22 AM, Patrick Williams pdw0...@gmail.com wrote:

Hi so I am making a bit of code to extract a bit of numbers data from a file
and then find the average of that data, however while I can get the code to
extract each specific piece of data I need, I can't seem to get the numbers
to add separately  so I can get a proper average. My sum1 variable seems to
only take the last bit of data entered. I was just wondering if anyone knows
what I'm doing wrong, the course I'm following hadn't started using regex
(or even proper lists) at this point, so there must be a way to do it
without. here's the code. the average of the data should be 0.6789 or
something, but I get 0.0334343 or something.

count=0
lst=list()


`lst = []` is the preferred syntax.


fname='mbox-short.txt'
fhand=open(fname)
for line in fhand:
 if line.startswith('X-DSPAM-Confidence:'):
 count=count+1
 colpos=line.find(':')
 zpos=line.find('0',colpos)
 num=float(line[zpos:50])
 sum1=0+num
 avg=float(sum1)/int(count)


I'll assume unless someone tells me differently that sum1 does not need 
reinitialising every time, and that avg needs to be calculated when the 
loop has finished.



print 'Count-', count,'--', 'Average-', avg

Any help at all is appreciated, and thanks in advance.



I don’t know what file you used, but the message you sent got this
header from Gmail, and the format doesn’t seem to be much different:


X-Spam-Evidence: '*H*': 0.79; '*S*': 0.00; 'separately': 0.09;
'wrong,': 0.09; 'subject:question': 0.10; 'code.': 0.18;
'variable': 0.18; 'bit': 0.19; 'advance.': 0.19; 'seems': 0.21;
'8bit%:5': 0.22; 'print': 0.22; 'skip:l 30': 0.24; '\xa0so': 0.24;
[snip 11 more lines]

(replaced tabstops with spaces)

Can you guess what’s wrong in your code?

You are reading only the first line. 


What does for line in fhand: do then?

--
Steve is going for the pink ball - and for those of you who are 
watching in black and white, the pink is next to the green. Snooker 
commentator 'Whispering' Ted Lowe.


Mark Lawrence

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Re: [Tutor] Hi, First question

[Steve Willoughby]

On 16-Jun-2013, at 09:21, Mark Lawrence breamore...@yahoo.co.uk wrote:

 On 16/06/2013 16:55, Chris “Kwpolska” Warrick wrote:
 On Sat, Jun 15, 2013 at 7:22 AM, Patrick Williams pdw0...@gmail.com wrote:
 Hi so I am making a bit of code to extract a bit of numbers data from a file
 and then find the average of that data, however while I can get the code to
 extract each specific piece of data I need, I can't seem to get the numbers
 to add separately  so I can get a proper average. My sum1 variable seems to
 only take the last bit of data entered. I was just wondering if anyone knows
 what I'm doing wrong, the course I'm following hadn't started using regex
 (or even proper lists) at this point, so there must be a way to do it
 without. here's the code. the average of the data should be 0.6789 or
 something, but I get 0.0334343 or something.
 
 count=0
 lst=list()
 
 `lst = []` is the preferred syntax.
 
 fname='mbox-short.txt'
 fhand=open(fname)
 for line in fhand:
 if line.startswith('X-DSPAM-Confidence:'):
 count=count+1
 colpos=line.find(':')
 zpos=line.find('0',colpos)
 num=float(line[zpos:50])
 sum1=0+num
 avg=float(sum1)/int(count)
 
 I'll assume unless someone tells me differently that sum1 does not need 
 reinitialising every time, and that avg needs to be calculated when the loop 
 has finished.
 
 print 'Count-', count,'--', 'Average-', avg
 
 Any help at all is appreciated, and thanks in advance.
 
 
 I don’t know what file you used, but the message you sent got this
 header from Gmail, and the format doesn’t seem to be much different:
 
 X-Spam-Evidence: '*H*': 0.79; '*S*': 0.00; 'separately': 0.09;
'wrong,': 0.09; 'subject:question': 0.10; 'code.': 0.18;
'variable': 0.18; 'bit': 0.19; 'advance.': 0.19; 'seems': 0.21;
'8bit%:5': 0.22; 'print': 0.22; 'skip:l 30': 0.24; '\xa0so': 0.24;
 [snip 11 more lines]
 (replaced tabstops with spaces)
 
 Can you guess what’s wrong in your code?
 
 You are reading only the first line. 
 
 What does for line in fhand: do then?

I think what that was referring to was the assumption that you're reading mail 
header lines from that file, and they can be split out over multiple lines (see 
the example cited above).  If that's the case, then for line in fhand will 
iterate over each line in the file, but you're only looking for lines which 
start with X-Spam-.. which would only be the FIRST part of the header if it's 
split out like that.

If your file is NOT organized like that, then your situation is different.  
However, if your files are like that, you're going to randomly miss data if the 
fields you're looking for don't happen to be on the first line of the 
multi-line header.

Now if you are reading RFC-822 (et al) standard mail messages in those files, 
there are bits of the Python standard library which will be immensely useful to 
you in parsing out those headers rather than trying to do it yourself.  That's 
something you're going to find to be the case frequently with Python.
 
 
 -- 
 Steve is going for the pink ball - and for those of you who are watching in 
 black and white, the pink is next to the green. Snooker commentator 
 'Whispering' Ted Lowe.
 
 Mark Lawrence
 
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Re: [Tutor] Hi, First question

[Alan Gauld]

On 15/06/13 06:22, Patrick Williams wrote:

Hi so I am making a bit of code to extract a bit of numbers data from a
file and then find the average of that data, however while I can get the
code to extract each specific piece of data I need, I can't seem to get
the numbers to add separately  so I can get a proper average. My sum1
variable seems to only take the last bit of data entered.




for line in fhand:
 if line.startswith('X-DSPAM-Confidence:'):
 count=count+1
 colpos=line.find(':')
 zpos=line.find('0',colpos)
 num=float(line[zpos:50])
 sum1=0+num


Are you sure that last line is right?

Its effectively just doing

sum1 = num

adding zero does nothing interesting.

So sum1 ends up at whatever num was at the end of the loop.

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

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[Tutor] Hi Folks...Need help with a modified version of the Subset sum problem.

[spiff007]

Hi there Tutor folks

I need your help with a modified version of the subset sum problem [
http://en.wikipedia.org/wiki/Subset_sum_problem].

The problem i am facing is a bit hard to describe (as most complex problem
always are :D ), so please bear with my longish articulation :)

Here it goes :

After scrubbing some input data, i have two lists 'minutes' (elements are
positive integers)  'names' (elements are strings). They are the exact
same length and each element of one corresponds exactly with the respective
element of the other.

The elements in the minutes list are not unique; a sample list is :
minutes = [60, 45, 30, 45, 45, 5, 60, 45, 30, 30, 45, 60, 60, 45, 30, 30,
60, 30, 30 ]
names = ['abc', 'ghi', 'jkl', 'def', 'zab', 'wux', ... ]

Now i need to pick some elements from the 'minutes' list (i.e. a subset of
minutes) which add up to a certain sum ('target_sum1').
I have to then do some processing with the *respective elements from the
'names' list, corresponding to, the elements i just picked from the
'minutes' list which sum upto target_sum1.*

I now have to remove these elements i picked (which add up to 'target_sum1'
) from the 'minutes' list, and essentially do a second pass, picking some
elements, which add up to a certain other sum ('target_sum2'). Again, *retrieve
the elements from the 'names' list*, *corresponding to the elements i just
picked which sum upto 'target_sum2'*,   do some processing on them.  And
so  on.

Picking a subset of numbers, which add up to a certain target sum, is a
well-known problem[1]  i have found the following code for it [2] :

I also have the code on a github gist
https://gist.github.com/anonymous/5620886

def subset_sum_recursive(numbers,target,partial):
s = sum(partial)

#check if the partial sum is equals to target
if s == target:
print sum(%s)=%s%(partial,target)
if s = target:
return # if we reach the number why bother to continue

for i in range(len(numbers)):
n = numbers[i]
remaining = numbers[i+1:]
subset_sum_recursive(remaining,target,partial + [n])

def subset_sum(numbers,target):
#we need an intermediate function to start the recursion.
#the recursion starts with an empty list  as partial solution.
subset_sum_recursive(numbers,target,list())

if __name__ == __main__:
minutes = [3,9,8,4,5,7,10]
target_sum = 15
subset_sum(minutes,target_sum)

#Outputs:
#sum([3, 8, 4])=15
#sum([3, 5, 7])=15
#sum([8, 7])=15
#sum([5, 10])=15


This above code returns the elements of the 'minutes' list(subset of the
'minutes' list)  which add up to 'target_sum'.

*I am stuck on this point : *
*I am unable to determine the list indices, of the elements of 'minutes'
which add upto 'target_sum1', so i can retrieve the corresponding elements
from the 'names' list,  do my processing on them.*
*
*
*I also need the list indices to remove the elements which add upto
target_sum1, and then run a second pass, to determine the elements which
add upto 'target_sum2'.*

Any  all explanations/links/code
snippets/thoughts/ideas/suggestions/feedback/comments/ of the Python tutor
community would be greatly appreciated.

Thanks a ton,
calvin
spiff...@gmail.com



References

1. http://en.wikipedia.org/wiki/Subset_sum_problem
2. http://stackoverflow.com/a/4633515/559456
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Re: [Tutor] Hi Folks...Need help with a modified version of the Subset sum problem.

[Peter Otten]

spiff007 wrote:

 Hi there Tutor folks
 
 I need your help with a modified version of the subset sum problem [
 http://en.wikipedia.org/wiki/Subset_sum_problem].
 
 The problem i am facing is a bit hard to describe (as most complex problem
 always are :D ), so please bear with my longish articulation :)
 
 Here it goes :
 
 After scrubbing some input data, i have two lists 'minutes' (elements are
 positive integers)  'names' (elements are strings). They are the exact
 same length and each element of one corresponds exactly with the
 respective element of the other.
 
 The elements in the minutes list are not unique; a sample list is :
 minutes = [60, 45, 30, 45, 45, 5, 60, 45, 30, 30, 45, 60, 60, 45, 30, 30,
 60, 30, 30 ]
 names = ['abc', 'ghi', 'jkl', 'def', 'zab', 'wux', ... ]
 
 Now i need to pick some elements from the 'minutes' list (i.e. a subset of
 minutes) which add up to a certain sum ('target_sum1').
 I have to then do some processing with the *respective elements from the
 'names' list, corresponding to, the elements i just picked from the
 'minutes' list which sum upto target_sum1.*
 
 I now have to remove these elements i picked (which add up to
 'target_sum1' ) from the 'minutes' list, and essentially do a second pass,
 picking some elements, which add up to a certain other sum
 ('target_sum2'). Again, *retrieve the elements from the 'names' list*,
 *corresponding to the elements i just
 picked which sum upto 'target_sum2'*,   do some processing on them.  And
 so  on.
 
 Picking a subset of numbers, which add up to a certain target sum, is a
 well-known problem[1]  i have found the following code for it [2] :
 
 I also have the code on a github gist
 https://gist.github.com/anonymous/5620886
 
 def subset_sum_recursive(numbers,target,partial):
 s = sum(partial)
 
 #check if the partial sum is equals to target
 if s == target:
 print sum(%s)=%s%(partial,target)
 if s = target:
 return # if we reach the number why bother to continue
 
 for i in range(len(numbers)):
 n = numbers[i]
 remaining = numbers[i+1:]
 subset_sum_recursive(remaining,target,partial + [n])
 
 def subset_sum(numbers,target):
 #we need an intermediate function to start the recursion.
 #the recursion starts with an empty list  as partial solution.
 subset_sum_recursive(numbers,target,list())
 
 if __name__ == __main__:
 minutes = [3,9,8,4,5,7,10]
 target_sum = 15
 subset_sum(minutes,target_sum)
 
 #Outputs:
 #sum([3, 8, 4])=15
 #sum([3, 5, 7])=15
 #sum([8, 7])=15
 #sum([5, 10])=15
 
 
 This above code returns the elements of the 'minutes' list(subset of the
 'minutes' list)  which add up to 'target_sum'.
 
 *I am stuck on this point : *
 *I am unable to determine the list indices, of the elements of 'minutes'
 which add upto 'target_sum1', so i can retrieve the corresponding elements
 from the 'names' list,  do my processing on them.*

I think the easiest approach is to combine the two lists into a single one

pairs = zip(names, minutes)

or, if you really need the indices

pairs = list(enumerate(minutes))

and invoke subset_sum() with these pairs instead of minutes alone.
Of course you have to modify the sum() call to unpack the pairs:

s = sum(value for index, value in partial)

 *I also need the list indices to remove the elements which add upto
 target_sum1, and then run a second pass, to determine the elements which
 add upto 'target_sum2'.*
 
 Any  all explanations/links/code
 snippets/thoughts/ideas/suggestions/feedback/comments/ of the Python tutor
 community would be greatly appreciated.
 
 Thanks a ton,
 calvin
 spiff...@gmail.com
 
 
 
 References
 
 1. http://en.wikipedia.org/wiki/Subset_sum_problem
 2. http://stackoverflow.com/a/4633515/559456


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Re: [Tutor] Hi

[Alan Gauld]

Luke Pettit petl...@gmail.com wrote

I was interested in which video tutorials Glen was watching, and if 
anyone

else could recommend some video tutorials to watch,


I don;t know what Glen was watching but thhere are a whole bunch of
videos at showmedo.com

Alan G.


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Re: [Tutor] Hi

[Luke Pettit]

Thanks Alan I found those about an hour ago :)

On 6 November 2010 20:11, Alan Gauld alan.ga...@btinternet.com wrote:


 Luke Pettit petl...@gmail.com wrote


  I was interested in which video tutorials Glen was watching, and if anyone
 else could recommend some video tutorials to watch,


 I don;t know what Glen was watching but thhere are a whole bunch of
 videos at showmedo.com

 Alan G.


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-- 
Luke Pettit
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Re: [Tutor] Hi

[Glen Clark]

Luke,

I used a video from Lynda.com, simply because I already had a
subscription. The price was about $25 per month which I think is more
expensive that showmedo. Or you could buy it for $99 (Python 3 Essential
Training (DVD-ROM)). 

The video's were very good for me personally because he was straight to
the point which kept me from getting bored. 

I have recently found showmedo though and they does loog very good also.
It seems to have a lot of content on there.

Regards, 
Glen

On Sat, 2010-11-06 at 21:29 +1100, Luke Pettit wrote:
 Thanks Alan I found those about an hour ago :)
 
 On 6 November 2010 20:11, Alan Gauld alan.ga...@btinternet.com
 wrote:
 
 Luke Pettit petl...@gmail.com wrote
 
 
 I was interested in which video tutorials Glen was
 watching, and if anyone
 else could recommend some video tutorials to watch,
 
 
 I don;t know what Glen was watching but thhere are a whole
 bunch of
 videos at showmedo.com
 
 Alan G.
 
 
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Re: [Tutor] Hi

[Glen Clark]

Also, if you have not yet chosen an IDE I recommend eclipse with the
pydev extension. Google them or if you use gnu/linux (like ubuntu) you
can get it from the package manager. It is a very simple interface, with
syntax highlighting, debug mode and console. 

On Sat, 2010-11-06 at 14:45 +, Glen Clark wrote:
 Luke,
 
 I used a video from Lynda.com, simply because I already had a
 subscription. The price was about $25 per month which I think is more
 expensive that showmedo. Or you could buy it for $99 (Python 3 Essential
 Training (DVD-ROM)). 
 
 The video's were very good for me personally because he was straight to
 the point which kept me from getting bored. 
 
 I have recently found showmedo though and they does loog very good also.
 It seems to have a lot of content on there.
 
 Regards, 
 Glen
 
 On Sat, 2010-11-06 at 21:29 +1100, Luke Pettit wrote:
  Thanks Alan I found those about an hour ago :)
  
  On 6 November 2010 20:11, Alan Gauld alan.ga...@btinternet.com
  wrote:
  
  Luke Pettit petl...@gmail.com wrote
  
  
  I was interested in which video tutorials Glen was
  watching, and if anyone
  else could recommend some video tutorials to watch,
  
  
  I don;t know what Glen was watching but thhere are a whole
  bunch of
  videos at showmedo.com
  
  Alan G.
  
  
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Re: [Tutor] Hi

[trench]

I'd also point out that Google has created a very awesome Python course
which is heavily dependent on video lectures by Nick Parlante. Included in
the course are downloadable exercises and examples (all mentioned in the
video lectures). After you review all of this quality (not to mention free)
material... I think you'll fully understand what separates Google from its
competitors. (By this, I simply mean that you will not see similar offerings
from, say, Facebook, Apple, or MS.)

http://code.google.com/edu/languages/google-python-class/index.html

http://code.google.com/edu/languages/google-python-class/index.htmlThis is
a part of Google's Google Code University. Here's the root URL for the
entire project: http://code.google.com/edu/  -- definitely worth checking
out.

-trench

On Fri, Nov 5, 2010 at 8:12 PM, Luke Pettit petl...@gmail.com wrote:

 Hi everyone,
 I'm just about to begin to learn python and have bookmarked a number of
 sites to learn from
 http://www.alan-g.me.uk/ is the main one but after reading this

 On Nov 4, 2010, at 3:10 PM, Glen Clark gle...@gmail.com wrote:

 Hello,

 I have completed my first python script. This is after watching a video
 guide on python and is my first attempt at writing code in python. While the
 code is not very useful I got the idea for it when googling python projects
 for beginners.


 I was interested in which video tutorials Glen was watching, and if anyone
 else could recommend some video tutorials to watch, mainly because of a mild
 dyslexia and preference for video tutorials.

 I have been learning Autodesk 3d Studio Max
 http://south-apac.autodesk.com/adsk/servlet/pc/index?siteID=1157326id=15474303
  for
 several years and learning it's scripting language Maxscript
 http://rosettacode.org/wiki/Category:MAXScript and since Autodesk now own
 all the competitors software and they all (except Max) use Python for
 their coding I thought it would be the way to go when learning a new
 language. Blender also uses Python btw.

 My 3d site http://lukepettit-3d.blogspot.com/

 --
 Luke Pettit

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Re: [Tutor] Hi

[Luke Pettit]

Wow information overload lol Thanks everyone this is great.

On 7 November 2010 13:43, trench trenchc...@gmail.com wrote:

 I'd also point out that Google has created a very awesome Python course
 which is heavily dependent on video lectures by Nick Parlante. Included in
 the course are downloadable exercises and examples (all mentioned in the
 video lectures). After you review all of this quality (not to mention free)
 material... I think you'll fully understand what separates Google from its
 competitors. (By this, I simply mean that you will not see similar offerings
 from, say, Facebook, Apple, or MS.)

 http://code.google.com/edu/languages/google-python-class/index.html

 http://code.google.com/edu/languages/google-python-class/index.htmlThis
 is a part of Google's Google Code University. Here's the root URL for the
 entire project: http://code.google.com/edu/  -- definitely worth checking
 out.

 -trench

 On Fri, Nov 5, 2010 at 8:12 PM, Luke Pettit petl...@gmail.com wrote:

 Hi everyone,
 I'm just about to begin to learn python and have bookmarked a number of
 sites to learn from
 http://www.alan-g.me.uk/ is the main one but after reading this

 On Nov 4, 2010, at 3:10 PM, Glen Clark gle...@gmail.com wrote:

 Hello,

 I have completed my first python script. This is after watching a video
 guide on python and is my first attempt at writing code in python. While the
 code is not very useful I got the idea for it when googling python projects
 for beginners.


 I was interested in which video tutorials Glen was watching, and if anyone
 else could recommend some video tutorials to watch, mainly because of a mild
 dyslexia and preference for video tutorials.

 I have been learning Autodesk 3d Studio Max
 http://south-apac.autodesk.com/adsk/servlet/pc/index?siteID=1157326id=15474303
  for
 several years and learning it's scripting language Maxscript
 http://rosettacode.org/wiki/Category:MAXScript and since Autodesk now own
 all the competitors software and they all (except Max) use Python for
 their coding I thought it would be the way to go when learning a new
 language. Blender also uses Python btw.

 My 3d site http://lukepettit-3d.blogspot.com/

 --
 Luke Pettit

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 - t




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[Tutor] Hi

[Luke Pettit]

Hi everyone,
I'm just about to begin to learn python and have bookmarked a number of
sites to learn from
http://www.alan-g.me.uk/ is the main one but after reading this

On Nov 4, 2010, at 3:10 PM, Glen Clark gle...@gmail.com wrote:

Hello,

I have completed my first python script. This is after watching a video
guide on python and is my first attempt at writing code in python. While the
code is not very useful I got the idea for it when googling python projects
for beginners.


I was interested in which video tutorials Glen was watching, and if anyone
else could recommend some video tutorials to watch, mainly because of a mild
dyslexia and preference for video tutorials.

I have been learning Autodesk 3d Studio Max
http://south-apac.autodesk.com/adsk/servlet/pc/index?siteID=1157326id=15474303
for
several years and learning it's scripting language Maxscript
http://rosettacode.org/wiki/Category:MAXScript and since Autodesk now own
all the competitors software and they all (except Max) use Python for
their coding I thought it would be the way to go when learning a new
language. Blender also uses Python btw.

My 3d site http://lukepettit-3d.blogspot.com/

-- 
Luke Pettit
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Re: [Tutor] Hi everybody stuck on some error need help please thank you!!

[Dave Angel]

(Don't top-post.  Either put your remarks immediately after the part 
they reference, or at the end of the message.  Otherwise, everything's 
thoroughly out of order.)


Marco Rompré wrote:

I tried to enter model = Modele (nom_fichier) but it still does not work.
  
You didn't define the global nom_fichier till after that line.  In 
general, while you're learning, please avoid using the same names for 
global values, class attributes, instance attributes, function parameter 
names, and local variables.   The rules for what a name means changes 
depending on where the name is used.

snip
On Fri, Apr 23, 2010 at 11:22 PM, Steven D'Aprano st...@pearwood.infowrote:

  

On Sat, 24 Apr 2010 01:07:11 pm Marco Rompré wrote:



Here's my code:
  

[...]


class Modele:

La definition d'un modele avec les magasins.

def __init__(self, nom_fichier, magasins =[]):
self.nom_fichier = nom_fichier
self.magasins = magasins
  

[...]


if __name__ == '__main__':
modele = Modele()
  
This is where you got the error, because there's a required argument, 
for parameter nom_fichier.  So you could use

   modele = Modele(thefile.txt)

nom_fichier = magasinmodele.txt
  
I'd call this something else, like  g_nom_fichier.  While you're 
learning, you don't want to get confused between the multiple names that 
look the same.

modele.charger(nom_fichier)
if modele.vide():
modele.initialiser(nom_fichier)
modele.afficher()

And here's my error :

Traceback (most recent call last):
  File F:\School\University\Session 4\Programmation
SIO\magasingolfmodele.py, line 187, in module
modele = Modele()
TypeError: __init__() takes at least 2 arguments (1 given)
  

You define Modele to require a nom_fichier argument, but then you try to
call it with no nom_fuchier.
snip



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[Tutor] Hi everybody stuck on some error need help please thank you!!

[Marco Rompré]

Hi everybody, I would appreciate your help on this one
In this program I want to create 2 concepts each with 2 or 3 properties
My first concept is magasin(shop in french) and my shop has 3 attributes:
nom(name in french), items and ville (city in french)
the second one is items and its 2 attributes are nom(name in french) and
prix (price in french)
I want to be able to show a modele with the name of my magasins (stores) and
the city theyre located in, what are the names of the items i have in each
magasin and their prices.

Here's my code:

class Magasin:

Le concept magasin pour la gestion d'inventaire des items de golf.

def __init__(self, nom =, items =[], ville= ):
self.nom = nom
self.items = items
self.vile = ville

def set_nom(self, nom):
self.nom = nom

nom = property(None, set_nom)

def set_items(self, items):
self.items = items

items = property(None, set_items)

def set_ville(self, ville):
self.ville = ville

items = property(None, set_ville)

def __str__(self):
return self.nom

class Item:

Le concept item pour la gestion d'inventaire des items de golf.

def __init__(self, nom =, prix = 100):
self.nom = nom
self.prix = prix

def set_nom(self, nom):
self.nom = nom

nom = property(None, set_nom)

def set_prix(self, prix):
self.prix = prix

prix = property(None, set_prix)

def __str__(self):
return self.nom

class Modele:

La definition d'un modele avec les magasins.

def __init__(self, nom_fichier, magasins =[]):
self.nom_fichier = nom_fichier
self.magasins = magasins

def set_nom_fichier(self, nom_fichier):
self.nom_fichier = nom_fichier

nom_fichier = property(None, set_nom_fichier)

def set_magasins(self, magasins):
self.magasins = magasins

magasins = property(None, set_magasins)

def sauvegarder(self):
modele_fichier = open(self.nom_fichier, 'w')
for magasin in self.magasins:
modele_fichier.write(===MAGASIN===  + \n)
modele_fichier.write(nom :  + magasin.nom + \n)
modele_fichier.write(items :  + \n)
for item in magasin.items:
modele_fichier.write(---ITEM---  + \n)
modele_fichier.write(nom :  + item.nom + \n)
modele_fichier.write(prix :  + item.prix + \n)
modele_fichier.write(---FIN ITEM---  + \n)
modele_fichier.write(===FIN MAGASIN===  + \n)
modele_fichier.close()

def charger(self):
magasins = []
try:
modele_fichier = open(self.nom_fichier, 'r')
except IOError:
print(Le fichier  + self.nom_fichier +  n'existe pas.)
else:
fin_fichier = False
while not fin_fichier:
ligne = modele_fichier.readline()
if ligne == :
self.set_magasins(magasins)
modele_fichier.close()
fin_fichier = True
break
magasin = Magasin()
items = []
fin_magasin = False
while not fin_magasin:
ligne = modele_fichier.readline().strip()
if ligne.startswith(===FIN MAGASIN===):
magasin.set_items(items)
magasins.append(magasin)
fin_magasin = True
elif ligne.startswith(nom):
nom = ligne.split(':')[1]
magasin.set_nom(nom.strip())
elif ligne.startswith(---ITEM---):
item = Item()
fin_item = False
while not fin_item:
ligne = modele_fichier.readline().strip()
if ligne.startswith(nom):
nom = ligne.split(':')[1]
item.set_nom(nom.strip())
elif ligne.startswith(prix):
prix = ligne.split(':')[1]
item.set_prix(float())
elif ligne.startswith(---FIN ITEM---):
items.append(item)
fin_item = True

def vide(self):
if self.magasins == []:
return True
else:
return False

def initialiser(self):

magasin01 = Magasin (Swing de golf)

magasin02 = Magasin (Golftown)

magasin03 = Magasin (PointGolf)


item01 = Item (Ensemble de fers Titleist)
item01.set_prix(1099.99)

item02 = Item (Ensemble de fers Callaway)
item02.set_prix(1299.99)

item03 = Item (Ensemble de fers Taylormade Burner Graphite)
item03.set_prix(2499.99)

 

Re: [Tutor] Hi everybody stuck on some error need help please thank you!!

[Steven D'Aprano]

On Sat, 24 Apr 2010 01:07:11 pm Marco Rompré wrote:

 Here's my code:
[...]
 class Modele:
 
 La definition d'un modele avec les magasins.
 
 def __init__(self, nom_fichier, magasins =[]):
 self.nom_fichier = nom_fichier
 self.magasins = magasins
[...]
 if __name__ == '__main__':
 modele = Modele()
 nom_fichier = magasinmodele.txt
 modele.charger(nom_fichier)
 if modele.vide():
 modele.initialiser(nom_fichier)
 modele.afficher()

 And here's my error :

 Traceback (most recent call last):
   File F:\School\University\Session 4\Programmation
 SIO\magasingolfmodele.py, line 187, in module
 modele = Modele()
 TypeError: __init__() takes at least 2 arguments (1 given)


You define Modele to require a nom_fichier argument, but then you try to 
call it with no nom_fuchier.


Also, I see that you do this:

def __init__(self, nom_fichier, magasins =[]):

You probably shouldn't do this -- it doesn't do what you probably think 
it does.

You probably think that what happens is that if you call 
Modele(nom_fichier), the magasins attribute will be set to an empty 
list. But that's not what happens.

Default values in Python are defined when the method is created, not 
when it is run. Watch this example:

 class Test:
... def __init__(self, x=[]):
... self.x = x
...
 a = Test()
 a.x
[]
 b = Test()
 b.x
[]

 a.x.append(Surprise!)
 b.x
['Surprise!']


How does this happen? Because every instance shares the same default 
list. When you append to it, all the other instances see the same 
change.

You don't notice this with default values that are strings or numbers, 
because you can't modify them, only replace them:

 x = y = 2  # Make two variables that point to the same value.
 x is y  # Make sure they are identical, not just equal.
True
 x = 3  # Make x point to something else.
 x is y  # And no longer identical.
False

 x = y = []  # Make two variables that point to the same thing.
 x is y
True
 x.append('something')  # Modify that list in place.
 x is y  # Still identical.
True
 y
['something']


If this is the behaviour you want, then you don't need to do anything. 
Otherwise you need to move the creation of the empty list inside the 
method:

def __init__(self, nom_fichier, magasins=None):
if magasins is None:
magasins = []
self.nom_fichier = nom_fichier
self.magasins = magasins



-- 
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Re: [Tutor] Hi everybody stuck on some error need help please thank you!!

[Marco Rompré]

I tried to enter model = Modele (nom_fichier) but it still does not work.
And for the list I don't understand very well, Do you know where I can pay
someone to help with my programming.
Because I feel to annoy tutors with my basic stuff

On Fri, Apr 23, 2010 at 11:22 PM, Steven D'Aprano st...@pearwood.infowrote:

 On Sat, 24 Apr 2010 01:07:11 pm Marco Rompré wrote:

  Here's my code:
 [...]
  class Modele:
  
  La definition d'un modele avec les magasins.
  
  def __init__(self, nom_fichier, magasins =[]):
  self.nom_fichier = nom_fichier
  self.magasins = magasins
 [...]
  if __name__ == '__main__':
  modele = Modele()
  nom_fichier = magasinmodele.txt
  modele.charger(nom_fichier)
  if modele.vide():
  modele.initialiser(nom_fichier)
  modele.afficher()
 
  And here's my error :
 
  Traceback (most recent call last):
File F:\School\University\Session 4\Programmation
  SIO\magasingolfmodele.py, line 187, in module
  modele = Modele()
  TypeError: __init__() takes at least 2 arguments (1 given)


 You define Modele to require a nom_fichier argument, but then you try to
 call it with no nom_fuchier.


 Also, I see that you do this:

 def __init__(self, nom_fichier, magasins =[]):

 You probably shouldn't do this -- it doesn't do what you probably think
 it does.

 You probably think that what happens is that if you call
 Modele(nom_fichier), the magasins attribute will be set to an empty
 list. But that's not what happens.

 Default values in Python are defined when the method is created, not
 when it is run. Watch this example:

  class Test:
 ... def __init__(self, x=[]):
 ... self.x = x
 ...
  a = Test()
  a.x
 []
  b = Test()
  b.x
 []
 
  a.x.append(Surprise!)
  b.x
 ['Surprise!']


 How does this happen? Because every instance shares the same default
 list. When you append to it, all the other instances see the same
 change.

 You don't notice this with default values that are strings or numbers,
 because you can't modify them, only replace them:

  x = y = 2  # Make two variables that point to the same value.
  x is y  # Make sure they are identical, not just equal.
 True
  x = 3  # Make x point to something else.
  x is y  # And no longer identical.
 False
 
  x = y = []  # Make two variables that point to the same thing.
  x is y
 True
  x.append('something')  # Modify that list in place.
  x is y  # Still identical.
 True
  y
 ['something']


 If this is the behaviour you want, then you don't need to do anything.
 Otherwise you need to move the creation of the empty list inside the
 method:

def __init__(self, nom_fichier, magasins=None):
if magasins is None:
 magasins = []
self.nom_fichier = nom_fichier
self.magasins = magasins



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Re: [Tutor] Hi everybody stuck on some error need help please thank you!!

[Steven D'Aprano]

On Sat, 24 Apr 2010 01:33:46 pm Marco Rompré wrote:
 I tried to enter model = Modele (nom_fichier) but it still does not
 work. 

What does still does not work mean?

Please copy and paste the error you get.



 And for the list I don't understand very well, 


Open an interactive session and do some experiments.

 a = []  # One empty list.
 b = []  # A different empty list. 
 a.append(1)  # Appends to the first list.
 print a, b
[1] []

 a = []  # An empty list.
 b = a  # The SAME empty list.
 a.append(1)
 print a, b
[1] [1]


When you have a default value like magasins=[], it is like the second, 
not the first.



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[Tutor] Hi there!

[Marco Rompré]

Hi! Does anyone of you know where to find all the solutions of Gerard
Swinnen Python tutorial exercises 

In the tutorial we just have the solutions to half of the exercises.

Thank you

-- 
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Re: [Tutor] Hi there :.)

[Alan Gauld]

mark-irel...@msn.com wrote 


Just introducing myself to say hiHi!


Hi welcome, but please don't include lots of attachments. 
It blows up people's mailboxes and bandwidth allowances.

Better to post them on a website and send a link.


I'm very new to programming, ...
place to start I found out that python and C++ are the usual 
starting place 


Actually there are many: VisualBasic, Lisp/Scheme and Java 
are all common starting points too. And each has its own 
merits depending on what you want to do.


but when I found out that civilisation and eve are programmed 
using python (my favorite type of games), that helped make the 
decision. 


As good a reason as any! :-)

My first aim is to get comfortable with python and move on 
to C++ (apparently python is slow ?!?). 


It is all relative. If you want to write fast moving graphics etc 
then yes, you probably need C++. For anything else you might 
find Python is fast enough.


The problem i'm having with this is with the platform. 
I want the ball to fall if it goes off the edge but be able to 
jump when on the platform. it either will fall off the edge 
but won't jump or it will jump but it won't fall. 
I don't want to change the way the controls are worked 
(with the true/ false).


test.py is the one file that didn't show up (at least for me)
Lots of demos but no test.py.

It is probably best if you can create the simplest possible
example that shows the problem rather than expecting folks 
to read through half a dozen fairly big files and try to guess 
what the design looks like etc. (That may have beeen 
what test.py was!)


Try to send some specific code that causes a problem, 
or at least that you think is causing the problem. 
Plus any error messages. It would help to tell us 
which OS and Python version you are using too.


HTH,

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


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[Tutor] hi everyone!

[malathi selvaraj]

i am new one to this programming language.

i like to learn python,what i do?

what i do to learn python in proper manner.



-- 
Regards,
S.Malathi.
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Re: [Tutor] hi everyone!

[Alan Gauld]

malathi selvaraj malathira...@gmail.com wrote


i am new one to this programming language.


Hello and welcome.


what i do to learn python in proper manner.


First of all make sure you download Python v2.6 
rather than v3. v3 is not ideal for learning just yet

it is still rather new.

Do you know any other programming language?
If so go to the official tutorial on the python web site 
(or download the docs) and work through it. That should 
be enough to get you started. Ask questions here, 
show us the code and any errors you get (in full)


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


If this is your first programming language then well 
done, you made a good choice! :-)


Go to here:

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

pick a tutorial(not the official one!) and work 
through it.  Every time you get stuck - and you will, so 
don't worry - send a question here explaining what is 
bugging you and any code plus error messages. (It 
also helps to mention the Python version, the OS and 
the tutorial you are using)


Either way have fun.


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


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[Tutor] HI

[Vishnu S]

Sir/Madame,
i'm a begginner to Python
help me in putting the first step to this world

With regards

Vishnu S
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Re: [Tutor] HI

[A.T.Hofkamp]

Vishnu S wrote:

Sir/Madame,
i'm a begginner to Python
help me in putting the first step to this world


Welcome!

A useful first page may be http://wiki.python.org/moin/BeginnersGuide for an 
overview, and http://wiki.python.org/moin/BeginnersGuide/NonProgrammers where 
you can find a lot of links to Python tutorials. Read one you like, download 
Python, and start experimenting and/or solving exercises and/or solving 
problems you like to solve.


When you get stuck, explain us your problem (usually wih a example program), 
and we will try to answer your question.


Albert

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[Tutor] Hi,

[Kgotlelelo Legodi]

Hi,
I am trying to write a program in python that solves a system of nonlinear 
equations using newton's method. I don't know what I am doing wrong. Please help
 
from scipy import*
 
x = array([0.0,0.0,0.0])
n=len(x)
tol= 0.1
N=30
 
k=1
while k = N:
def f(x):
f= zeros((len(x)),float)
f[0][k]= x[0][k]**2 + x[1][k]-37
f[1][k]=x[0][k]- x[1][k]**2- 5
f[2][k]= x[0][k] + x[1][k]+ x[2][k]- 3
return f[k]
def J(x):
J= zeros((n,n),float)
for i in range(n):
ei=zeros(n,float)
ei[i]=1.0
J[:i]=(f(x[k]+tol*ei)-f(x[k]))/tol
return J
 
y[k] = -(J.I)*f[k]
x[k+1]=x[k]+y[k]
 
if sqrt(dot(f0,f0)/len(x))  tol: print x
else:
k=k+1
 
print 'Too many iterations'

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Re: [Tutor] Hi,

[bob gailer]

Kgotlelelo Legodi wrote:

Hi,
I am trying to write a program in python that solves a system of 
nonlinear equations using newton's method. I don't know what I am 
doing wrong. Please help


Mostly what you are doing wrong is failing to tell us why you think 
there is a problem! What results are you expecting and what are you getting?


 
from scipy import*
 
x = array([0.0,0.0,0.0])

n=len(x)
tol= 0.1
N=30
 
k=1

while k = N:
def f(x):
f= zeros((len(x)),float)
f[0][k]= x[0][k]**2 + x[1][k]-37
f[1][k]=x[0][k]- x[1][k]**2- 5
f[2][k]= x[0][k] + x[1][k]+ x[2][k]- 3
return f[k]
def J(x):
J= zeros((n,n),float)
for i in range(n):
ei=zeros(n,float)
ei[i]=1.0
J[:i]=(f(x[k]+tol*ei)-f(x[k]))/tol
return J
 
y[k] = -(J.I)*f[k]

x[k+1]=x[k]+y[k]
 
if sqrt(dot(f0,f0)/len(x))  tol: print x

else:
k=k+1
 
print 'Too many iterations'






--
Bob Gailer
Chapel Hill NC
919-636-4239
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[Tutor] Hi

[Eddie]

Hi, I'm new and just starting to learn Python. Just testing if this
works or not and if anybody reads it lol.
Eddie
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Re: [Tutor] Hi

[Kent Johnson]

On Mon, Jun 8, 2009 at 7:30 AM, Eddieeddie9...@gmail.com wrote:
 Hi, I'm new and just starting to learn Python. Just testing if this
 works or not and if anybody reads it lol.

Yes, it works. Welcome!

Kent
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Re: [Tutor] Hi

[Christian Witts]

Eddie wrote:

Hi, I'm new and just starting to learn Python. Just testing if this
works or not and if anybody reads it lol.
Eddie
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Welcome to the list and enjoy your stay. :)

--
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Christian Witts


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Re: [Tutor] Hi

[Alan Gauld]

Eddie eddie9...@gmail.com wrote 


Hi, I'm new and just starting to learn Python. Just testing if this
works or not and if anybody reads it lol.


Welcome! If you take a look at the archive on the web site 
you'll see that quite a lot of folks read it   - and many reply too!


You might even find answers to a lot of your own questions :-)

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


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Re: [Tutor] Hi everyone

[Lie Ryan]

Doug Reid wrote:

Now here is the code I'm having trouble following:
 
while word:

position = random.randrange(len(word))
jumble += word[position]
word = word[:position] + word[(position + 1):]
 
position = random.randrange(len(word)). This will create a starting 
point for the program to pick a letter out of a word at random using the 
length of the word as a range I think. Like if the word is 'python' and 
since it has 6 letters, random.randrange(len(word)) will pick a random 
starting point such as the letter 'y' for example. It's gonna be inside 
a while loop, so the next time it runs, 'python' will be 'pthon' and the 
random range will be 5 letters and on down till there is no more 
letters, is this right?


`position` is an integer. It is the index of the letter we want to put 
into `jumble`. The first line generates a random index, the second line 
copies the letter and append it to `jumble`, and the third line removes 
that letter from `word`.


Ok, so everyone of the letters that was 'extracted' from the word 
'python' will be put into the variable 'jumble' that was defined as empty.
 
This is the part that troubles me:
 
word = word[:position] + word[(position + 1):]


How do we remove a single letter? In python, string is immutable; we 
must create a new string that has the required property (i.e. letter in 
`position` removed).


Rather than removing, we copied the part of string before `position` 
(word[:position]) and after `position` (word[position+1:]) and 
concatenating them together to become our new `word`.


How does the slicing works?

The standard model for slicing and indexing in python is like this:

-6  -5  -4  -3  -2  -1
 +---+---+---+---+---+---+
 | p | y | t | h | o | n |
 +---+---+---+---+---+---+
 0   1   2   3   4   5   6

Let's say `position` is 3 (i.e. the letter h).

word[:3] is:

-6  -5  -4  -3  -2  -1
 +---+---+---+---+---+---+
 | p | y | t | h | o | n |
 +---+---+---+---+---+---+
 0   1   2   3   4   5   6
 |___|
   word[0:3]

which is pyt

while

word[3+1:] - word[4:] is:

 -6  -5  -4  -3  -2  -1
 +---+---+---+---+---+---+
 | p | y | t | h | o | n |
 +---+---+---+---+---+---+
 0   1   2   3   4   5   6
 |___|
 word[4:6]

which is on

concatenating pyt + on, we get pyton (i.e. h removed)


An extended version of the line that may be more easily digestible:

letters_before_position = word[:position]
letters_after_position = word[position+1:]
word = letters_before_position + letters_after_position


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Re: [Tutor] Hi everyone

[spir]

Le Wed, 20 May 2009 18:25:07 -0700 (PDT),
Doug Reid rnrcr...@yahoo.com s'exprima ainsi:

 The next line in the loop,
word = word[:position] + word[(position + 1):]
 
 creates a new version of word minus the one letter at position position.
 Using slicing, the computer creates two new strings from word. The first
 slice, word[:position], is every letter up to, but not including,
 word[position]. The next slice, word[(position + 1):], is every letter
 after word[position]. These two string are joined together and assigned to
 word, which is now equal to its old self, minus the one letter
 word[position].

Can someone explain this in simpler terms? I'm sorry this
 is so lengthy for my first post:) 

It's confusing because abstract and without any example. In the case you wrote 
where the word is python, the letter 'y', and so the position is 1, you get:
wordpython
word[:position] p
word[position+1:]   thon
glued together  pthon
Also, a confusing part of the program id the loop header:

while word:
    position = random.randrange(len(word))
    jumble += word[position]
    word = word[:position] + word[(position + 1):]

In python, a container such as a string is considered 'False' when it's empty. 
Right? So that the loop header above is equivalent to:
while len(word)  0:
and the loop will stop when every letter has been extracted from the word.

Denis
--
la vita e estrany
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Re: [Tutor] Hi everyone

[W W]

On Thu, May 21, 2009 at 2:42 AM, spir denis.s...@free.fr wrote:

 snip
while word:
 position = random.randrange(len(word))
jumble += word[position]
word = word[:position] + word[(position + 1):]


Something that many of us use for debugging, and is also useful for
comprehension is a simple print statement. If you were to convert the loop
to this:

while word:
position = random.randrange(len(word))
   jumble += word[position]
   word = word[:position] + word[(position + 1):]
   print jumble
   print word
   # Optional - for further understanding
   print word[:position]
   print word[(position+1):]

you would basically see what Denis wrote - only every step through the loop.

HTH,
Wayne

p.s. - When you start graphical programming, I'd look at pyglet or pygame.
Although to really understand event driven programming, it really helped me
to start writing programs with Tkinter. YMMV
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Re: [Tutor] Hi everyone....thanks for the help

[Doug Reid]

Thank you all for the help.  I believe I understand now, and think this will be 
a great group to learn from.
 
Doug


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[Tutor] Hi everyone

[Doug Reid]

Hi,
 
I'm teaching myself Python mainly for to use as a hobby.  I'd like to do 
graphical programs eventually and maybe some simple graphic games.  I feel I'm 
doing well with the tutorial I'm using but it would be nice to have some real 
people to ask questions and opinions, so on that note, I'm having a little 
trouble understanding the following code.  I grasp the basics of what it does 
but am wondering if someone could explain it in simpler terms..
 
In the tutorial, I'm using Tuples and there is a Word Jumble game given to show 
how this can be used.  A tuple of words is created:
 
WORDS = (python, jumble, easy, difficult, answer, xylophone)
correct=word
 
Then a variable that will hold the jumbled word is defined: jumble=' '
Ok, then a variable: word=random.choice(WORDS) is created to pick a random 
element from WORDS.  I get this part.
 
Now here is the code I'm having trouble following:
 
while word:
    position = random.randrange(len(word))
    jumble += word[position]
    word = word[:position] + word[(position + 1):]
 
position = random.randrange(len(word)). This will create a starting point for 
the program to pick a letter out of a word at random using the length of the 
word as a range I think. Like if the word is 'python' and since it has 6 
letters, random.randrange(len(word)) will pick a random starting point such as 
the letter 'y' for example. It's gonna be inside a while loop, so the next time 
it runs, 'python' will be 'pthon' and the random range will be 5 letters and on 
down till there is no more letters, is this right?
 
Ok, so everyone of the letters that was 'extracted' from the word 'python' will 
be put into the variable 'jumble' that was defined as empty.
 
This is the part that troubles me:
 
word = word[:position] + word[(position + 1):]
 
I know basically it is creating a new string through the while loop for 
extracint letters.  But I don't feel I understand it fully,  The expression is 
confusing to me.  Here is an excerpt from the tutorial that explains it and 
confuses me more:
 
The next line in the loop,
   word = word[:position] + word[(position + 1):]

creates a new version of word minus the one letter at position position. Using 
slicing, the computer creates two new strings from word. The first slice, 
word[:position], is every letter up to, but not including, word[position]. The 
next slice, word[(position + 1):], is every letter after word[position]. These 
two string are joined together and assigned to word, which is now equal to its 
old self, minus the one letter word[position].
 
Can someone explain this in simpler terms? I'm sorry this is so lengthy for my 
first post:)
 
Any help will be appreciated
 
Thanks,
 
Doug

 


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Re: [Tutor] HI, #Include like in python

[A.T.Hofkamp]

wesley chun wrote:

   import listen

You can use the __import__ function if you want, but generally you
want the import statement as above.  The equivalent to 'import listen'
is:

   listen = __import__('listen')

See the tutorial here: http://docs.python.org/tutorial/modules.html



you also have to make sure that your .py file is in one of the
folders/directories listed in sys.path (to see it, import sys then do
print sys.path). if the file is not in one of those folders, you will
also get an import error.

you can either add the correct directory to your PYTHONPATH
environment variable, or manually add it at run-time using
sys.path.append/insert.


A simpler form is to put listen.py and usbconnection.py in the same 
directory.

In the latter you can do something like


import listen

listener = listen.ListenClass(param1, param2)
listener.begin()  # Call the 'begin' method of the ListenClass object.


You can use the ListenClass like normal, just state that Python should look 
for it in the listen file.


Albert
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[Tutor] HI, #Include like in python

[andré palma]

Hi \o
I'm asking if there is any #include( C) like or any include('File.php') 
(php) like in python.
I have 2 files: usbconnection.py and listen.py, And i want to use 
some classes avaiable in listen.py on my main file usbconnection.py. 
I've tryed to do __import__(listen.py) but obviously it gave me an 
error... ImportError: No module named 
/home/andrefsp/projects/sigre/listen.py


So, if anybody knows how to do an include in python please reply me =)

Bye the way, i've sent an email in last week asking how to read data 
from USB port. So, i've finally did it, yesterday i was able to read 
data from my USB port, if anybody is interested in some information 
about it just need to ask, i don't mind to help


=)

it is impossible to make eggs without omelettes 
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[Tutor] hi...

[Alberto Perez]

I have a problem with python, I'm begginner in python. How clear the screen of 
GUI python interactive and which is the difference between interactive mode 
and not interactive mode because when I run a program in interactive mode, 
the program run very good, but if run in not interactive mode not show me 
error, but the return of function returns no value, this is the source code:
 
def suma(no1,no2):total=no1+no2return total
print 'hola'opcion=input()if opcion==1:print 'suma'a=input()
b=input()suma(a,b)
 
the result of this code is:
 
hola1suma57 totalTraceback (most recent call last):  File pyshell#0, 
line 1, in moduletotalNameError: name 'total' is not defined 
 
why this happens??? what I did wrong??? and why run very good in interactive 
mode??? thanks for help me and sorry for my bad english, I from Mexico and I 
english student. Thank you.
_
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Re: [Tutor] hi...

[bhaaluu]

On Sun, Aug 24, 2008 at 2:31 AM, Alberto Perez [EMAIL PROTECTED] wrote:
 I have a problem with python, I'm begginner in python. How clear the screen
 of GUI python interactive

I'm not sure what you mean by GUI interactive?
However, at the Python interactive prompt, I can
clear the screen using a simple,  old-fashioned way:

 for i in range(1,50):
 print(\n)

That prints 50 newlines, thus effectively clearing the screen.

Happy Programming!
-- 
b h a a l u u at g m a i l dot c o m
Kid on Bus: What are you gonna do today, Napoleon?
Napoleon Dynamite: Whatever I feel like I wanna do. Gosh!
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Re: [Tutor] hi...

[Alan Gauld]

Alberto Perez [EMAIL PROTECTED] wrote


. How clear the screen of GUI python interactive


bhaaaluu answered that


and which is the difference between interactive mode
and not interactive mode


WW answered that


because when I run a program in interactive mode,
the program run very good, but if run in not interactive
mode not show me error,


How are you running your program in non interactive mode
Are you using IDLE or Pythonwin? Or are you running it from
a command window? If you are running it from IDLE are you
creating a new file and typing in the code then saving it
and running it from the menu (or F5 key)?

That's what it looks like...


but the return of function returns no value


It returns a value but you don't print it.
One big difference between  and non interactive mode
is that the  prompt prints the values of expressions,
including function calls. Non interacticve mode does
not print these, you have to use print. (This is why in my
tutorial I always use print even in the  prompt; because
it avoids this confusion.)

Thus

print suma(a,b)

would show the result.

Or as WW said you could store the result in a variable called total

def suma(no1,no2):
   total=no1+no2
   return total

print 'hola'
opcion=input()# could replace with: opcion = input(hola\n)
if opcion==1:
  print 'suma'
  a=input()   # its good to give a prompt string of some kind
  b=input()
  print suma(a,b)


total

...

name 'total' is not defined

why this happens???


As the error says total is not defined in your shells namespace.
It only exists within your program. As WW said, it only exists inside
suma() in your code. Thasts why you need to create a global level
variable or just print the result of suma() directly.

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



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Re: [Tutor] hi...

[broek]

- Message from [EMAIL PROTECTED] -
Date: Sun, 24 Aug 2008 01:31:28 -0500
From: Alberto Perez [EMAIL PROTECTED]
Reply-To: Alberto Perez [EMAIL PROTECTED]
 Subject: [Tutor] hi...
  To: tutor@python.org


run a program in interactive mode, the program run very good, but if  
 run in not interactive mode not show me error, but the return of   
function returns no value, this is the source code:


def suma(no1,no2):   total=no1+no2
   return total
print 'hola'
opcion=input()
if opcion==1:
   print 'suma'
   a=input() b=input()
   suma(a,b)

the result of this code is:

hola
1
suma
5
7

total
Traceback (most recent call last):  File  pyshell#0, line 1, in  
moduletotalNameError: name 'total'  is not defined


why this happens??? what I did wrong??? and why run very good in



Hi,

Welcome to python and the tutor list.

An earlier response pointed out that you need to bind the returned  
value to total as in

total = suma(a, b)
but I thought a bit of explanation might help. In your function, you  
define total. That makes `total' a name in the scope of the function.  
That means that `total' can be seen by code in your function, but not  
code outside of your function.


This might seem confusing now, but in the long run, it makes life  
easier. How? Well, you can define all sorts of names in the body of  
your functions without having them clutter up the name-space of your  
overall code. That makes things cleaner. It also makes them less error  
prone. If total defined in  your function was visible everywhere by  
default, then you would have to make sure that your function didn't  
define any names that higher level code did. (You'd have to make sure  
that total defined in a function didn't overwrite total defined  
outside of the function.)


You can make names defined in functions be globally available, but  
until you've got some experience, don't do that. (Arguably, once you  
have experience, don't do that then either ;-)


Hope that helps some,

Brian vdB
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[Tutor] Hi

[Firoze Khan]

Hi,
  I want Tutors mailing List
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Re: [Tutor] Hi

[Kent Johnson]

Firoze Khan wrote:
 Hi,
   I want Tutors mailing List

You seem to have found it.

Kent
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Re: [Tutor] Hi

[bob gailer]

Firoze Khan wrote:
 Hi,
   I want Tutors mailing List
If you want to subscribe visit:

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


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Re: [Tutor] Hi,every one

[Sridhar Ratna]

On 6/23/07, Yang Yang [EMAIL PROTECTED] wrote:

 1.what is the best book for python study.

Try Byte of Python
  http://byteofpython.info/


 2.what's is the better IDE for python


Start off with IDLE, which comes with the Python installer. Go through
this IDLE tutorial,
  http://hkn.eecs.berkeley.edu/~dyoo/python/idle_intro/

(If you're not satisfied, there are numerous Python IDEs available)

-- 
http://srid.nearfar.org/
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[Tutor] Hi,every one

[Yang Yang]

i am a newman for python world

i have some word want to ask


1.what is the best book for python study.

2.what's is the better IDE for python



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Re: [Tutor] Hi,every one

[Rolando Pereira]

Yang Yang escreveu:
 i am a newman for python world
 
 i have some word want to ask
 
 
 1.what is the best book for python study.
 

I like Dive into Python.
( http://www.diveintopython.org/ )

 2.what's is the better IDE for python
 

That depends on what OS you are.

 
 Thanks for all
 
 
 
 
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Re: [Tutor] Hi

[Rikard Bosnjakovic]

On 3/16/07, Ben [EMAIL PROTECTED] wrote:

 Is anyone can point me where I can find a good tutorial about pywin for
 someone like me?

Pywin itself is not a package for making GUIs, it's merely a IDE for
Windows and got the win32all-package included.

For GUIs, you want to look at wxPython, pygtk or similiar packages.
Those will let you do what you are looking for.


-- 
- Rikard.
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[Tutor] hi, learning python

[Raven Of Night Raven Of Night]

print Guesses you've taken: ,i, \nGuess letter: 
letter_guess = raw_input()'


this is a line of my program, and raw_input only takes one argument. I want 
it to display like this

Guesses you've taken: 0
Guess letter: (letter would go here)

instead of

Guesses you've taken: 0
Guess letter:
(leter you've taken)

is there a way to continue the input line, like in java you would just do 
System.out.print?

thanks

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Re: [Tutor] hi, learning python

[Bob Gailer]

Raven Of Night Raven Of Night wrote:
 print Guesses you've taken: ,i, \nGuess letter: 
 letter_guess = raw_input()'


 this is a line of my program, and raw_input only takes one argument. I want 
 it to display like this

 Guesses you've taken: 0
 Guess letter: (letter would go here)

 instead of

 Guesses you've taken: 0
 Guess letter:
 (leter you've taken)

 is there a way to continue the input line, like in java you would just do 
 System.out.print?
   

print Guesses you've taken:  ,i 
letter_guess = raw_input(Guess letter: )



-- 
Bob Gailer
510-978-4454

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Re: [Tutor] hi, learning python

[Alan Gauld]

Raven Of Night Raven Of Night [EMAIL PROTECTED] wrote

print Guesses you've taken: ,i, \nGuess letter: 
letter_guess = raw_input()'


 this is a line of my program, and raw_input only takes one argument.

Yes, and that argument is the prompt to display to the user, which
is what you want...

letter_guess = raw_input('Guess letter. ')

 is there a way to continue the input line, like in java you would 
 just do
 System.out.print?

As to simulating Java's print style, yes, there are a couple of ways.

1) put a comma at the end of the string to be printed:

print 'hello ,
print 'world'

prints
hello world

2) use sys.stdout.write()

sys.stdout.write('hello ')
sys.stdout.write('world')

3) use string formatting to create the string before printing

outstring = %s %s % % (var1,var2,var3)

It all depends what you are trying to do which one suits best...

HTH,


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


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[Tutor] Hi, need help on terminal input

[Ramakrishnan, Shashikanth]

Hi,

Does anybody know how to create a pygtk widget which can
accept and diplay input from

a serial port?



Thanks and Rgds,

Shashikanth
Ramakrishnan

Embedded Product Division

Cell: +6-0122977087

e-mail :[EMAIL PROTECTED]








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