[Tutor] Trivia program.
Hi, I got a problem with this program.
name = raw_input("Hi. What's your name? ")called = name * 5print "\nIf a small child were trying to get your attention, " \ "your name would become:"print called
When i input the name like "John Goodman"
it prints like...
John GoodmanJohn GoodmanJohn GoodmanJohn GoodmanJohn Goodman
But i want to print it like...
John Goodman John Goodman John Goodman John Goodman John Goodman
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[Tutor] Re: Basic terminology
Bill Mill wrote: However, where will it be pointing in 16 hours? Well, in 12 hours it will be at the one, then four more hours later it will be pointing at the five. This can be represented as: 1 + (16 % 12) = 1 + 4 = 5 Correcter is (1 + 16) % 12 = 17 % 12 = 5 In general, the hour at some point in the future will be: (start time) + (hours in the future % 12) (start time + hours in the future) % 12 The difference can be seen in a small example: suppose it is 10 o'clock, and you want to know what it will be in 6 hours. Your formula gives 10 + (6 % 12) = 10 + 6 = 16 which is not correct (unless dealing with 24-hour systems of course, but that's not the case here) Correct is: (10 + 6) % 12 = 16 % 12 = 4 (In 24-hour systems, just replace 12 with 24) -- Codito ergo sum Roel Schroeven ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Trivia program.
Mmmhh ... one very simple way would be to replace your first line by : name = raw_input(Hi. What's your name? ) + But if you want to keep the name as it is, I bet the best way is to replace your second line by : called = .join([ name for i in xrange(5) ]) The advantage of this second method is theis added only *between* the names, and not after ... Pierre . Sm0kin'_Bull a écrit : Hi, I got a problem with this program. name = raw_input(Hi. What's your name? ) called = name * 5 print \nIf a small child were trying to get your attention, \ your name would become: print called When i input the name like John Goodman it prints like... John GoodmanJohn GoodmanJohn GoodmanJohn GoodmanJohn Goodman But i want to print it like... John Goodman John Goodman John Goodman John Goodman John Goodman How can I do it? Express yourself instantly with MSN Messenger! MSN Messenger http://g.msn.com/8HMBEN/2728??PS=47575 Download today it's FREE! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Pierre Barbier de Reuille INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP Botanique et Bio-informatique de l'Architecture des Plantes TA40/PSII, Boulevard de la Lironde 34398 MONTPELLIER CEDEX 5, France tel : (33) 4 67 61 65 77fax : (33) 4 67 61 56 68 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Trivia program.
On Feb 16, 2005, at 10:26, . Sm0kin'_Bull wrote:
it prints like...
John GoodmanJohn GoodmanJohn GoodmanJohn GoodmanJohn Goodman
But i want to print it like...
John Goodman John Goodman John Goodman John Goodman John Goodman
How can I do it?
Try replacing the called = name * 5 line with:
if not name.endswith(' '):
called = ((name + ' ') * 5).strip()
else:
called = (name * 5).strip()
-- Max
maxnoel_fr at yahoo dot fr -- ICQ #85274019
Look at you hacker... A pathetic creature of meat and bone, panting
and sweating as you run through my corridors... How can you challenge a
perfect, immortal machine?
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Re: [Tutor] Trivia program.
Or name = raw_input(Hi. What's your name? ) called = %s % name On Wed, 16 Feb 2005 11:46:09 +0100, Pierre Barbier de Reuille [EMAIL PROTECTED] wrote: Mmmhh ... one very simple way would be to replace your first line by : name = raw_input(Hi. What's your name? ) + But if you want to keep the name as it is, I bet the best way is to replace your second line by : called = .join([ name for i in xrange(5) ]) The advantage of this second method is theis added only *between* the names, and not after ... Pierre . Sm0kin'_Bull a écrit : Hi, I got a problem with this program. name = raw_input(Hi. What's your name? ) called = name * 5 print \nIf a small child were trying to get your attention, \ your name would become: print called When i input the name like John Goodman it prints like... John GoodmanJohn GoodmanJohn GoodmanJohn GoodmanJohn Goodman But i want to print it like... John Goodman John Goodman John Goodman John Goodman John Goodman How can I do it? Express yourself instantly with MSN Messenger! MSN Messenger http://g.msn.com/8HMBEN/2728??PS=47575 Download today it's FREE! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Pierre Barbier de Reuille INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP Botanique et Bio-informatique de l'Architecture des Plantes TA40/PSII, Boulevard de la Lironde 34398 MONTPELLIER CEDEX 5, France tel : (33) 4 67 61 65 77fax : (33) 4 67 61 56 68 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- 'There is only one basic human right, and that is to do as you damn well please. And with it comes the only basic human duty, to take the consequences. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] dictionary dispatch for object instance attributes question
Brian van den Broek wrote:
My Node class defines a _parse method which separates out the node
header, and sends those lines to a _parse_metadata method. This is where
the elif chain occurs -- each line of the metadata starts with a tag
like dt= and I need to recognize each tag and set the appropriate Node
object attribute, such as .document_type. (I do not want to rely on the
unhelpful names for the tags in the file format, preferring more
self-documenting attribute names.)
I've come up with *a* way to use a dictionary dispatch, but I'll wager a
great deal it isn't the *best* way.
Here is a minimal illustration of what I have come up with:
code
class A:
def __init__(self):
self.something = None
self.something_else = None
self.still_another_thing = None
def update(self, data):
for key in metadata_dict:
if data.startswith(key):
exec('''self.%s = %s''' %(metadata_dict[key],
data[len(key):]))
# triple quotes as there may be quotes in metadata
# values
break
metadata_dict = {'something_tag=': 'something',
'2nd_tag=': 'something_else',
'last=': 'still_another_thing'}
a = A()
print a.still_another_thing
a.update('last=the metadata value for the last= metadata tag')
print a.still_another_thing
/code
output
None
the metadata value for the last= metadata tag
/output
So, it works. Yay :-)
But, should I be doing it another way?
Another way to do this is to use dispatch methods. If you have extra processing to do for each tag,
this might be a good way to go.
I'm going to assume that your data lines have the form 'tag=data'. Then your Node class might have
methods that look like this:
class Node:
...
def parse_metadata(self, line):
tag, data = line.split('=', 1)
try:
handler = getattr(self, 'handle_' + tag)
except AttributeError:
print 'Unexpected tag:', tag, data
else:
handler(data)
def handle_something_tag(self, data):
self.something = int(data) # for example
def handle_last(self, data):
try:
self.another_thing.append(data) # attribute is a list
except AttributeError:
self.another_thing = [data]
and so on. This organization avoids any if / else chain and puts all the processing for each tag in
a single place.
BTW the try / except / else idiom is used here to avoid catching unexpected
exceptions. The naive
way to write it would be
try:
handler = getattr(self, 'handle_' + tag)
handler(data)
except AttributeError:
print 'Unexpected tag:', tag, data
The problem with this is that if handler() raise AttributeError you will get an unhelpful error
message and no stack trace. Putting the call to handler() in an else clause puts it out of the scope
of the try / except but it will still be executed only if the getattr succeeds.
Also, I know the general security concerns about things like exec. They
make me nervous in using it, even though I am (as yet) the sole user. Am
I right in thinking that the constrained way I am using it here protects
me? My code uses most of the attributes as a simple storage container
for later rewriting of the file, but in a few cases they enter into
(safe seeming) conditionals like:
if 'text' == self.document_type:
self.do_text_stuff()
if 'RTF' == self.document_type:
self.do_RTF_stuff()
Conditionals on a 'type' flag are a code smell that suggests using subclasses. Maybe you should have
a TextNode class and an RtfNode class. Then the above becomes just
self.do_stuff()
and TextNode and RtfNode each have the appropriate implementations of
do_stuff().
I'm not saying this is the right choice for you, just something you might
consider.
Kent
Thanks and best to all,
Brian vdB
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Re: [Tutor] best way to scrape html
You might find these threads on comp.lang.python interesting: http://tinyurl.com/5zmpn http://tinyurl.com/6mxmb Peter Kim wrote: Which method is best and most pythonic to scrape text data with minimal formatting? I'm trying to read a large html file and strip out most of the markup, but leaving the simple formatting like p, b, and i. For example: p class=BodyText style=MARGIN: 0in 0in 12ptfont face=Times New Romanb style=font-weight: normalspan lang=EN-GB style=FONT-SIZE: 12ptTrigger:/span/bspan lang=EN-GB style=FONT-SIZE: 12ptspan style=spacerun: yes#160;/span Debate on budget in Feb-Mar. New moves to cut medical costs by better technology./span/font/p I want to change the above to: pbTrigger:/b Debate on budget in Feb-Mar. New moves to cutmedical costs by better technology./p Since I wanted some practice in regex, I started with something like this: pattern = (?:)(.+?)(?: ?.*?)(.*?)(/\1) result = re.compile(pattern, re.IGNORECASE | re.VERBOSE | re.DOTALL).findall(html) But it's getting messy real fast and somehow the non-greedy parts don't seem to work as intended. Also I realized that the html file is going to be 10,000+ lines, so I wonder if regex can be used for large strings. So I'm thinking of using sgmllib.py (as in the Dive into Python example). Is this where I should be using libxml2.py? As you can tell this is my first foray into both parsing and regex so advice in terms of best practice would be very helpful. Thanks, Peter Kim ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] dictionary dispatch for object instance attributes question
Kent Johnson wrote:
Another way to do this is to use dispatch methods. If you have extra
processing to do for each tag, this might be a good way to go.
I'm going to assume that your data lines have the form 'tag=data'. Then
your Node class might have methods that look like this:
class Node:
...
def parse_metadata(self, line):
tag, data = line.split('=', 1)
try:
handler = getattr(self, 'handle_' + tag)
except AttributeError:
print 'Unexpected tag:', tag, data
else:
handler(data)
def handle_something_tag(self, data):
self.something = int(data) # for example
def handle_last(self, data):
try:
self.another_thing.append(data) # attribute is a list
except AttributeError:
self.another_thing = [data]
and so on. This organization avoids any if / else chain and puts all the
processing for each tag in a single place.
One more idea. If you have 20 different tags but only four different ways of processing them, maybe
you want to use a dict that maps from the tag name to a tuple of (attribute name, processing
method). With this approach you need only four handler methods instead of 20. It would look like this:
metadata_dict = {
'something_tag' : ( 'something', self.handle_int ),
'last' : ( 'another_thing', self.handle_list ),
}
def parse_metadata(self, line):
tag, data = line.split('=', 1)
try:
attr_name, handler = metadata_dict[tag]
except AttributeError:
print 'Unexpected tag:', tag, data
else:
handler(attr_name, data)
def handle_int(self, attr_name, data):
setattr(self, attr_name, int(data))
def handle_list(self, attr_name, data):
l = getattr(self, attr_name, [])
l.append(data)
setattr(self, attr_name, l)
I-have-to-stop-replying-to-my-own-posts-ly yours,
Kent
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Re: [Tutor] Queued threads
Not to beat a dead horse, but Liam Clarke wrote: Oops, you probably want to do this then- for i in range( 0, 3 ): oThread = Thread( target=mainFunction ).start() Thread.start() looks like it returns None. # In [23]: from threading import Thread In [24]: import time In [25]: def foo(): : print doing... : time.sleep(15) : print done : In [26]: t = Thread(target=foo).start() doing... In [27]: print t None In [28]: done In [28]: print t None In [29]: t = Thread(target=foo) In [30]: t.start() doing... In [31]: t.isAlive() Out[31]: True In [32]: done In [32]: t.isAlive() Out[32]: False # So, checking the return of Thread.start() doesn't seem like it would do what you think it would do. You probably want to get the thread object and check that directly with isAlive(). Oh, and if you spawn a bunch of threads at once and you want to wait until the all complete before doing something else, do something like this: # #create a list to contain the threads thread_list = [] for i in range(10): t = Thread(target=foo) print creating thread, t #put each thread in the list thread_list.append(t) #iterate over thread list and start each thread for t in thread_list: print starting thread, t t.start() #iterate over thread list and wait for each thread for t in thread_list: print waiting for thread, t while 1: if not t.isAlive(): break time.sleep(.2) # It'll give you output something like this: # creating thread Thread(Thread-35, initial) creating thread Thread(Thread-36, initial) creating thread Thread(Thread-37, initial) creating thread Thread(Thread-38, initial) creating thread Thread(Thread-39, initial) creating thread Thread(Thread-40, initial) creating thread Thread(Thread-41, initial) creating thread Thread(Thread-42, initial) creating thread Thread(Thread-43, initial) creating thread Thread(Thread-44, initial) starting thread Thread(Thread-35, initial) starting thread Thread(Thread-36, initial) starting thread Thread(Thread-37, initial) starting thread Thread(Thread-38, initial) doing... starting thread Thread(Thread-39, initial) doing... doing... starting thread Thread(Thread-40, initial) doing... starting thread doing... Thread(Thread-41, initial) doing... starting thread Thread(Thread-42, initial) starting thread Thread(Thread-43, initial) starting thread Thread(Thread-44, initial) doing... doing... doing... waiting for thread Thread(Thread-35, started) doing... done done done done done done waiting for thread Thread(Thread-36, stopped) waiting for thread Thread(Thread-37, stopped) waiting for thread done done done done Thread(Thread-38, stopped) waiting for thread Thread(Thread-39, stopped) waiting for thread Thread(Thread-40, stopped) waiting for thread Thread(Thread-41, stopped) waiting for thread Thread(Thread-42, stopped) waiting for thread Thread(Thread-43, stopped) waiting for thread Thread(Thread-44, stopped) # But in this situation, I totally agree with Max. You don't need threads for this. Just use os.system. You could use one of the popens (or the new subprocess module - never used that one myself), but os.system blocks until the called program exits. while oThread: print 'sleeping 3 seconds' time.sleep( 3 ) A if condition generally has an implicit else: pass clause as I think of it, so it will just keep reiterating if the condition isn't met. Jeremy Joens ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Problem with variables
wrote this, It's a bit lame thoughI = "Allen"me = "Allen"my = "Allen's"print \"""%s woke up early in the morning. But, it was unusal by %s. %s pillowwas with %s. %s didn't want to wake up But, %s tried my best and woke up.it was so amazing!""" % (I,me,my,me,I,I)raw_input("\n\\t\t\t- The End -")But it looks like this...Allen woke up early in the morning. But, it was unusal by Allen. Allen's pillowwas with Allen. Allen didn't want to wake up But, Allen tried my best and woke up.it was so amazing - The End -
the problem is about lining
I want it to print like this...
Allen woke up early in the morning. But, it was unusal by Allen.
Allen's pillow was with Allen. Allen didn't want to wake up But, Allen
tried my best and woke up. it was so amazing
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[Tutor] Problems in making calulating program.
I wrote this to add 2 numbers...print "Please input data"number1 = int(raw_input(" "))number2 = int(raw_input("+ "))total = number1 + number2print totalraw_input("")I want to make output like this...1 + 1 = 2But, actually... it looks like this...1+ 12
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Re: [Tutor] Problem with variables
. Sm0kin'_Bull wrote:
wrote this, It's a bit lame though
I = "Allen"
me = "Allen"
my = "Allen's"
print \
"""
%s woke up early in the morning. But, it was unusal by %s. %s pillow
was with %s. %s didn't want to wake up But, %s tried my best and woke
up.
it was so amazing!""" % (I,me,my,me,I,I)
raw_input("\n\\t\t\t- The End -")
But it looks like this...
Allen woke up early in the morning. But, it was unusal by Allen.
Allen's pillow
was with Allen. Allen didn't want to wake up But, Allen tried my best
and woke up.
it was so amazing
- The End -
the problem is about lining
I want it to print like this...
Allen woke up early in the morning. But, it was unusal by Allen.
Allen's pillow was with Allen. Allen didn't want to wake up But, Allen
tried my best and woke up. it was so amazing
This is what I got:
In [45]: I = "Allen"
In [46]: me = "Allen"
In [47]: my = "Allen's"
In [48]:
In [48]: print \
: """
: %s woke up early in the morning. But, it was unusal by %s. %s
pillow
: was with %s. %s didn't want to wake up But, %s tried my best
and woke up.
: it was so amazing!""" % (I,me,my,me,I,I)
Allen woke up early in the morning. But, it was unusal by Allen.
Allen's pillow
was with Allen. Allen didn't want to wake up But, Allen tried my best
and woke up.
it was so amazing!
It looks like it should. If you want it to show up exactly like posted
at the end, you need something more like this:
In [50]: print \
: """
: %s woke up early in the morning. But, it was unusal by %s.
: %s pillow was with %s. %s didn't want to wake up But, %s
: tried my best and woke up. it was so amazing!""" %
(I,me,my,me,I,I)
Allen woke up early in the morning. But, it was unusal by Allen.
Allen's pillow was with Allen. Allen didn't want to wake up But, Allen
tried my best and woke up. it was so amazing!
###
Jeremy Jones
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Re: [Tutor] Re: Basic terminology
On Wed, 16 Feb 2005 11:34:55 +0100, Roel Schroeven [EMAIL PROTECTED] wrote: Bill Mill wrote: However, where will it be pointing in 16 hours? Well, in 12 hours it will be at the one, then four more hours later it will be pointing at the five. This can be represented as: 1 + (16 % 12) = 1 + 4 = 5 Correcter is (1 + 16) % 12 = 17 % 12 = 5 d'oh! thanks for the correction. In general, the hour at some point in the future will be: (start time) + (hours in the future % 12) (start time + hours in the future) % 12 Peace Bill Mill bill.mill at gmail.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Case acceptance using raw_input
At 11:40 PM 2/15/2005, Alan Gauld wrote: Is there a better way for raw_input to accept both caps and lower case letters than: def aFunction(): action = raw_input(Perform an action?(y,n): ) action = raw_input(Perform an action?(y,n): ).upper() if action == 'y' or action == 'Y': if action == 'Y': anotherFunction() etc. Bob Gailer mailto:[EMAIL PROTECTED] 303 442 2625 home 720 938 2625 cell ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] dictionary dispatch for object instance attributes question
Kent Johnson said unto the world upon 2005-02-16 05:58: Brian van den Broek wrote: SNIP Kent's useful explanation of how to use handlers Also, I know the general security concerns about things like exec. They make me nervous in using it, even though I am (as yet) the sole user. Am I right in thinking that the constrained way I am using it here protects me? My code uses most of the attributes as a simple storage container for later rewriting of the file, but in a few cases they enter into (safe seeming) conditionals like: if 'text' == self.document_type: self.do_text_stuff() if 'RTF' == self.document_type: self.do_RTF_stuff() Conditionals on a 'type' flag are a code smell that suggests using subclasses. Maybe you should have a TextNode class and an RtfNode class. Then the above becomes just self.do_stuff() and TextNode and RtfNode each have the appropriate implementations of do_stuff(). I'm not saying this is the right choice for you, just something you might consider. Kent Hi Kent, thanks for the snipped discussion on handlers -- very useful. As for the code smell thing, I have a follow-up question. I now get the point of the type-based conditional being a smell for classes. (I get it due to a previous thread that an over-enthusiastic inbox purge prevents me from citing with certainty, but I think it was Bill and Alan who clarified it for me.) My problem is that I've got a lot of code which was written before I got that point and my code doesn't yet actually do much. (I do have working code for parsing my original source files and storing all of their metadata, etc., but I haven't yet got working code for doing the manipulating the data in the ways I want.) I had been thinking better to get everything working and then refactor. Is that an unsound approach? My worry about refactoring now is that I feel like I am rearranging deck-chairs when I should be worried about getting the ship to float :-) Thanks and best to all, Brian vdB ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] dictionary dispatch for object instance attributes question
Brian van den Broek wrote: As for the code smell thing, I have a follow-up question. I now get the point of the type-based conditional being a smell for classes. (I get it due to a previous thread that an over-enthusiastic inbox purge prevents me from citing with certainty, but I think it was Bill and Alan who clarified it for me.) My problem is that I've got a lot of code which was written before I got that point and my code doesn't yet actually do much. (I do have working code for parsing my original source files and storing all of their metadata, etc., but I haven't yet got working code for doing the manipulating the data in the ways I want.) I had been thinking better to get everything working and then refactor. Is that an unsound approach? My worry about refactoring now is that I feel like I am rearranging deck-chairs when I should be worried about getting the ship to float :-) It's a hard question because it really comes down to programming style and judgement. I like to work in a very incremental style - design a little, code a little, test a little, repeat as needed. I believe in 'Refactor Mercilessly' - another XP slogan. I have many years experience and a well-developed opinion of what is good design and bad design. One consequence of this style is, I usually have working code and tests to go with it. It may not do very much, but it works. So for me, if I smell something, and think that refactoring into subclasses - or some other change - is the best design for the problem as I understand it, I will probably do the refactoring. It's not going to be easier tomorrow :-) If it just smells a little, or the refactoring is major, I might think about how to get rid of the smell but put it off until I'm pretty sure it is a good idea. I don't think of this as rearranging the deck chairs - it's more like building the right foundation. Clean, expressive, well-designed code is a pleasure to work with. For you, it's probably not so cut-and-dried. If you don't have the experience to judge how bad a smell is, or to think through the possibilities so clearly, it's harder to know how to proceed. If you are in part dabbling with OOP design to learn about it, maybe you want to put off some changes until the code is working; then you could make the change and do a comparison and see which one feels cleaner to you. I hope this helps at least a little :-) Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Queued threads
On Wed, 16 Feb 2005 16:50:07 +1300, Liam Clarke [EMAIL PROTECTED] wrote: Oops, you probably want to do this then- for i in range( 0, 3 ): oThread = Thread( target=mainFunction ).start() while oThread: print 'sleeping 3 seconds' time.sleep( 3 ) Probably not. Note that, since oThread's value is not changed in the body of this while loop, you will either never execute the body (if oThread is false) or execute it infintely many times (if oThread is true). I doubt that's the desired behavior. ;) In this case, since Thread.start() apparently always returns None, the while loop is effectively a no-op. However, if it *did* get triggered, it would do so immediately after the first thread [which returned a true value from start()] was started -- preventing later threads from being started because the main program is stuck in this endless loop. You could perhaps rewrite the whole thing like this: .for i in range(3): .mythread = Thread(target=mainFunction) .mythread.start() .while mythread.isAlive(): .print sleeping 3 seconds [main thread] .time.sleep(3) Though as others have said, if you're not starting the second thread until the first is finished, then you might as well just make it explicitly sequental and not bother with threads: .for i in range(3): .mainFunction() If you actually want the threads to process concurrently, and simply wait until all of them are done, you could do this: .threadlist = [] .for i in range (3): .mythread = Thread(target=mainFunction) .mythread.start() .threadlist.append(mythread) .for thread in threadlist: .thread.join() The join() method will wait until that thread is finished, and then return. If the thread is already finished when it's called, it returns immediately. Jeff Shannon ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] dictionary dispatch for object instance attributes question
On Tue, 15 Feb 2005 23:48:31 -0500, Brian van den Broek [EMAIL PROTECTED] wrote: Jeff Shannon said unto the world upon 2005-02-15 21:20: On Tue, 15 Feb 2005 17:19:37 -0500, Brian van den Broek [EMAIL PROTECTED] wrote: For starters, I've made metadata a class attribute rather than an unconnected dictionary. This seems conceptually nicer to me. The problem is that my Node instance live in a TP_file class instance, and the way my code is now, the TP_file instance also needs to see the metadata dict. There are a few tags, which if present in any Node of the file make me want to treat the entire file a bit differently. (Of course, here is the place where my novice-designer status is most likely to be bitting me.) So, that's why I have it as a module level object, rather than within a class. (I do, however, see your point about it being neater.) Okay, that makes sense. You have two different classes (the TP_file class and the Node class) that need access to the same information, so yes, having it at the module level lets them share it more effectively. (Alternately, since it sounds like the TP_file class is where all of the Node instances are created, you *could* decide that the metadata belongs as part of the TP_file, which would then actively share it with Node... but what you've got sounds like a very reasonable plan, so at this point I wouldn't worry about it.) In addition, update() can now modify several attributes at once, at the cost of a bit of extra parsing up front. The metadata all occurs one element to a line in my original file. [...] Maybe I'm still missing a better way, but as I am processing line by line, each line with one element, I don't see how to use this cool looking multiple elements at once approach. Yes, if you know that you will only have one header per line, then it's reasonable to process them one line at a time. You could alternatively have the TP_file gather all the header lines for a given node into a list, and then process that list to create the Node instance, but given the specifics of your case you probably wouldn't gain anything over your current approach by doing so. This is what makes programming so interesting -- there's so many different choices possible, and which one is best depends on a large number of factors. When writing a program for some task, the best design for a particular set of circumstances may be completely different than the best design for a somewhat different particular set of circumstances -- and the best design for general usage is probably an altogether different thing still. Good luck! Jeff Shannon ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: ****SPAM(11.2)**** [Tutor] Larger program organization
On Fri, 11 Feb 2005, Bob Gailer wrote: Whenever you find yourself writing an if statement ask whether this would be better handled by subclasses. Whenever you find yourself about to write a global statement, consider making the variables properties of a class. Bob -- Brian already asked for an explanation of your first statement, and I found the ensuing discussion very instructive. Can you explain the second? As an aesthetic point, I hate globals, and I'd love a discussion with some examples of using class variables as a way of avoiding this. Terry ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Help needed with script to batch-create shapefiles
Dear all, I have several thousand files in dBaseIV format that I need to convert to shapefiles for use in ArcGIS. I've written a script (see below) to automate this process but thus far have been unable to get it to work. I suspect that there's a simple reason for this, but I'm a complete novice with Python and have been unable to find it. Any help would be greatly appreciated! Regards, Chris Bromley ##Script Name: dBase Table to Shapefile ##Description: Converts dBase files to shapefiles ##Created By: Chris Bromley. ##Date: 16/02/2005 # Import system modules import sys, string, os, win32com.client # Create the Geoprocessor object gp = win32com.client.Dispatch(esriGeoprocessing.GpDispatch.1) try: # Load required toolboxes... gp.AddToolbox(C:/Program Files/ArcGIS/ArcToolbox/Toolboxes/Conversion Tools.tbx) gp.AddToolbox(C:/Program Files/ArcGIS/ArcToolbox/Toolboxes/Data Management Tools.tbx) #Define create variables to contain the source files and output file location paths gp.workspace = C:\PhD\ElwhaRiverProject\Physical_modelling\Model_Data_Corrected\Tester3\One out_workspace = C:\PhD\ElwhaRiverProject\Physical_modelling\Model_Data_Corrected\Tester3 # Get a list of the dBase tables in the workspace fcs = gp.ListTables(*,dBase) # Loop through the list of feature classes fcs.reset() fc = fcs.next() while fc: # Set the output filename for each output to be the same as the input filename output = out_workspace + fc # Process: Make XY Event Layer... gp.MakeXYEventLayer_management(fc, x, y, output, ) # Process: Feature Class To Shapefile (multiple)... gp.FeatureClassToShapefile_conversion(output, out_workspace, ) fc = fcs.next() except: gp.AddMessage(gp.GetMessages(2)) print gp.GetMessages(2) This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] dictionary dispatch for object instance attributes question
Kent Johnson said unto the world upon 2005-02-16 15:02: Brian van den Broek wrote: SNIP I had been thinking better to get everything working and then refactor. Is that an unsound approach? My worry about refactoring now is that I feel like I am rearranging deck-chairs when I should be worried about getting the ship to float :-) It's a hard question because it really comes down to programming style and judgement. I like to work in a very incremental style - design a little, code a little, test a little, repeat as needed. I believe in 'Refactor Mercilessly' - another XP slogan. I have many years experience and a well-developed opinion of what is good design and bad design. One consequence of this style is, I usually have working code and tests to go with it. It may not do very much, but it works. So for me, if I smell something, and think that refactoring into subclasses - or some other change - is the best design for the problem as I understand it, I will probably do the refactoring. It's not going to be easier tomorrow :-) If it just smells a little, or the refactoring is major, I might think about how to get rid of the smell but put it off until I'm pretty sure it is a good idea. I don't think of this as rearranging the deck chairs - it's more like building the right foundation. Clean, expressive, well-designed code is a pleasure to work with. For you, it's probably not so cut-and-dried. If you don't have the experience to judge how bad a smell is, or to think through the possibilities so clearly, it's harder to know how to proceed. If you are in part dabbling with OOP design to learn about it, maybe you want to put off some changes until the code is working; then you could make the change and do a comparison and see which one feels cleaner to you. I hope this helps at least a little :-) Kent Hi Kent, I see my `strike that' msg. didn't get through in time, to save you from the reply. But, from the selfish perspective, I'm glad enough about that; the above does indeed help more than a little. I get, in the abstract at least, how Test Driven Development would make these refactorings much easier to do with confidence. (Somewhere near half the point, isn't it?) The goal of my current project, beyond the given of having useful code, is to write a medium sized project in OOP. At the outset, I felt I had to choose between getting a handle on OOP or TDD. I felt I could only tackle one new paradigm at a time. I went with OOP as I didn't want to spend the effort of getting procedural code down using TDD and then have to redo it in OOP. But, not having test does make the refactoring more scary than I imagine it would be tests in hand. And I would have had the need to redo it, I think. The file format I am working with is from an application I've been using as a PIM/Knowledge manager for several years. So, I've got tons of data and tons of plans. I'm not certain if the term is the right one, but I'm thinking of the code I am working on as a base toolset or `framework' for all the other things I want to do with the files of that format. Thus, subclassing and other OOP techniques are sure to be important for those plans. But, I think you hit it right on the head -- my inexperience with OOP doesn't provide me with any metric for judgement about these things. Browsing through things like Fowler, Beck, Brant, Opdyke's _Refactoring_, while fun, doesn't help much without my having struggled with my own OOP code first. Hey, yesterday I proved that having read about setattr numerous times is no guarantee I'll remember it the first time a use case comes up :-) Thanks for the continued efforts to help me `get' it. Best to all, Brian vdB ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Help needed with script to batch-create shapefiles
Chris, On Wed, 16 Feb 2005 21:37:10 +, Chris Bromley [EMAIL PROTECTED] wrote: Dear all, I have several thousand files in dBaseIV format that I need to convert to shapefiles for use in ArcGIS. I've written a script (see below) to automate this process but thus far have been unable to get it to work. I suspect that there's a simple reason for this, but I'm a complete novice with Python and have been unable to find it. Any help would be greatly appreciated! Regards, Chris Bromley snip script What you've written translates, in newsgroup-speak, to Will somebody write this script for me that I need? Boil your question down into something smaller, and then ask it with the appropriate information. I suggest reading http://www.catb.org/~esr/faqs/smart-questions.html . Peace Bill Mill bill.mill at gmail.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] dictionary dispatch for object instance attributes question
Jeff Shannon said unto the world upon 2005-02-16 16:09: On Tue, 15 Feb 2005 23:48:31 -0500, Brian van den Broek [EMAIL PROTECTED] wrote: SNIP some of Jeff's responses to my evaluation of his earlier suggestions Yes, if you know that you will only have one header per line, then it's reasonable to process them one line at a time. You could alternatively have the TP_file gather all the header lines for a given node into a list, and then process that list to create the Node instance, but given the specifics of your case you probably wouldn't gain anything over your current approach by doing so. This is what makes programming so interesting -- there's so many different choices possible, and which one is best depends on a large number of factors. When writing a program for some task, the best design for a particular set of circumstances may be completely different than the best design for a somewhat different particular set of circumstances -- and the best design for general usage is probably an altogether different thing still. Good luck! Jeff Shannon Thanks Jeff, the confirmation that my assessment made sense is very helpful. Due to the my lack of experience (as discussed in my response to Kent) I'm always uncomfortable rejecting a proposed solution -- is my assessment that the solution isn't the best a product of that inexperience, or am I on to something? So, thanks for taking the time to `bless' my assessment. Best to all, Brian vdB ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: ****SPAM(11.2)**** [Tutor] Larger program organization
Terry Carroll said unto the world upon 2005-02-16 16:18: On Fri, 11 Feb 2005, Bob Gailer wrote: Whenever you find yourself writing an if statement ask whether this would be better handled by subclasses. Whenever you find yourself about to write a global statement, consider making the variables properties of a class. Bob -- Brian already asked for an explanation of your first statement, and I found the ensuing discussion very instructive. Can you explain the second? As an aesthetic point, I hate globals, and I'd love a discussion with some examples of using class variables as a way of avoiding this. Terry Hi Terry and all, I'm probably not the best person to explain this, but I've got a use case that might help illustrate. The thing that finally got me to write my first Class statement was a procedural program where I had a hard to find bug. I wrote a debug_report function which would print out an informative report about the state of all the objects I suspected were implicated in the bug. Then, I put debug_report calls at the suspicious places. But, my procedural code had function call chains 4 or 5 links deep, and at no level did any of the functions have access to all of the objects of interest. To make it work in purely procedural, I had to either make many objects global or litter my functions with passing objects up and down as parameters that weren't needed for the function's tasks, but simply so debug_report could see them. I made a class, put my functions in it, and suddenly, they all could `see' the objects of interest without the passing and returning of objects just for the sake of visibility. Some `self's sprinkled around did the work instead. So, even if you don't make use of further OOP features (as I am learning to do on other threads), classes give you a namespace option between globals and locals -- `continentals' if you like ;-) HTH, and looking forward to more expert explanations, Brian vdB ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Help needed with script to batch-create shapefiles
On Wed, 16 Feb 2005, Bill Mill wrote: I have several thousand files in dBaseIV format that I need to convert to shapefiles for use in ArcGIS. I've written a script (see below) to automate this process but thus far have been unable to get it to work. I suspect that there's a simple reason for this, but I'm a complete novice with Python and have been unable to find it. Boil your question down into something smaller, and then ask it with the appropriate information. I suggest reading http://www.catb.org/~esr/faqs/smart-questions.html . Hi Chris, Yes, at the moment, without even a clue what kind of problem there is, there's little we can do. We don't have dBase on our system, so the kind of diagnostics we have access to is limited to what you tell us. *grin* We just don't have enough information, and telling us that something is going wrong isn't enough for us to do a good analysis. Let's try pinpointing what you mean by not working. I notice that your code has the following structure: ### try: ## .. do a bunch of stuff except: gp.AddMessage(gp.GetMessages(2)) print gp.GetMessages(2) ### This is a blanket try/except block that catches everything. This kind of exception handler tends to disguise problems in the code that have nothing to do with dBaseIV. I'm also not sure at all if it's the right thing for the program to ignore the error and try to continue working with the 'gp' object. Try to make exceptional conditions yell out when an exception occurs. That may make it much easier to see the problems at hand. Can you add the following import to your program? ### import traceback ### Also modify the except block to this: ### try: ## .. do a bunch of stuff except: traceback.print_exc() ### These changes use the excellent 'traceback' error-tracing module: http://www.python.org/doc/lib/module-traceback.html and traceback.print_exc() will print out the details of errors that occur in the try block. We have to do what we can to get some useful information what's going wrong, before continuing to work on this problem. Good luck to you! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Help needed with script to batch-create shapefiles
On Wed, 16 Feb 2005 21:37:10 +, Chris Bromley [EMAIL PROTECTED] wrote: Any help would be greatly appreciated! Others have already pointed out that we will have a hard time helping without a bit more information. But I've noticed something odd in your code -- it probably doesn't have anything to do with your problem, but it seems like an awkward idiom to me. fc = fcs.next() while fc: # [...] fc = fcs.next() This, it seems to me, is equivalent to (but less readable than) the following: .for fc in fcs: .# [...] If you're going to do something with every member of a list, then it's much more straightforward to use a for loop (which automatically tracks the iteration) than to use a while loop and manually adjusting the loop-controlling expression. Actually, it occurs to me that this *might* cause a confusing result in your code. Presuming that fcs is a standard iterator (as your usage of next() suggests), then calling next() on an exhausted iterator will raise a StopIteration exception. The for loop will automatically handle that, but with your while loop it would be caught by the following bare except statement. That means that you'll run (what I presume to be) your error-handling code even when you successfully convert every member of fcs... Jeff Shannon ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Larger program organization
Terry Carroll wrote: On Fri, 11 Feb 2005, Bob Gailer wrote: Whenever you find yourself writing an if statement ask whether this would be better handled by subclasses. Whenever you find yourself about to write a global statement, consider making the variables properties of a class. Bob -- Brian already asked for an explanation of your first statement, and I found the ensuing discussion very instructive. Can you explain the second? As an aesthetic point, I hate globals, and I'd love a discussion with some examples of using class variables as a way of avoiding this. Global variables are one way to make state persist across function calls. Here's a toy example that might give you the idea. Suppose you want to write a function that keeps a running total. You could do something like this (not recommended!): total = 0 def addToTotal(inc): global total total += inc Every time you call addToTotal, total is incremented. This is already a poor design. - There is no encapsulation - to increment the total, you call a function, to view the total you look at the global variable. - There is no API - to reset the total you would have to set the global variable. You could try to fix this by adding more functions: def printTotal(): print 'Total is', total def resetTotal(): global total total = 0 That's a little better, maybe. But there are other problems: - You can only have one total. What if you want two different totals? - Your global namespace has extra names - total, addToTotal, etc. For short scripts this structure can work, but for larger projects it gets unwieldy. OOP to the rescue! How about a Total class? class Total: def __init__(self): self.reset() def add(self, inc): self.total += inc def print(self): print 'Total is', self.total def reset(self): self.total = 0 You can use this like this: t = Total() t.inc(5) t.print() t.reset() Now everything is wrapped up in a nice neat package. There is a clear, consistent API, no namespace pollution, and you have a reusable object. You might also be interested in this essay: http://www.pycs.net/users/323/stories/15.html Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Active Python
Hi, I am not a programmer, but have decided to learn Python. I am wondering if anyone has used the Activestate ActivePython and what are the advantages/disadvantages of using it rather than the standard Python tools. Robert ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Reading/writing Wave files
After looking at the Python docs for the wave module, I'm a bit puzzled as to how to use it. Does anyone have an example I can browse? If I write to a wave file, is the data I write actually audible, if I use Winamp or some other wave player, or is it more complicated than that? Is the data I write actually part of the content of the wave file, or do I have to manually handle the file structure of the wave file too (the part that is unique to wave files, that is)? thanks ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
