Re: ten small Python programs

2007-06-08 Thread Jacob Hallen
In article [EMAIL PROTECTED],
Steve Howell  [EMAIL PROTECTED] wrote:
I've always thought that the best way to introduce new
programmers to Python is to show them small code
examples.  

Something like this:

http://www.lava.se/sam/

Jacob Hallén

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Re: ten small Python programs

2007-05-29 Thread stef

   
 Secondly, Python is nowadays not only used by
 programmers,
 but also by e.g. Scientific users (former MatLab
 users),
 who are not interested in the code itself,
 but just in the results of that particular code.
 For these people a lot of example programs,
 for which they can easily see the results,
 make some small changes and see the result again,
 would be a wonderful addition.

 

 In your own personal use, what are some
 libraries/techniques/etc. that you think could benefit
 from some kind of more organized presentation of
 example programs (or better way of showing how the
 examples work, etc.)?
for example SciPy,
but I think it yield for all libs/techniques.
And I guess Windows users have a much greater need for such an 
organization than *nix users.
   Are you part of the Scientific
 community?

   
sort of, I indeed work at a university,
but not doing scientific work myself,
I work on a supporting department.

 How new are you to Python?
very new ;-)
(I've lot of experience in a other programming languages,
last years mostly Delphi, JAL, MatLab)

   I do think
 newbies/intermediates/advanceds all have different
 needs.
   
agreed.

cheers,
Stef Mientki
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Re: ten small Python programs

2007-05-28 Thread Stef Mientki
Steve Howell wrote:
 I've always thought that the best way to introduce new
 programmers to Python is to show them small code
 examples.  
 
This is really a nice piece of missing Python.

Sorry I didn't follow this thread accurately,
but have you considered to produce an example environment like in wxPython ?

The wxPython demo program is written as an interactive tutorial,
with a few hundred examples, nicely ordered in groups.
The user can view the demo, the code and the help text.
The user can also change the code and see the results right away.

It would even be nicer, if everybody could drop her/his examples
in a standard way, so they would be automatically incorporated in
something like the wxPython interactive demo.

cheers,
Stef Mientki
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Re: ten small Python programs

2007-05-28 Thread Kay Schluehr
Just for the amusement of the audience. The following is a reusable
testscript:

 def add_money(amounts):
... pennies = sum([round(int(amount * 100)) for amount in amounts])
... return float(pennies / 100.0)
...
 add_money([0.13, 0.02]) == 0.15
0.14999
 add_money([0.13, 0.02]) == 0.15
True
 assert add_money([0.13, 0.02]) == 0.15
 assert add_money([100.01, 99.99]) ==  200
 assert add_money([0, -13.00, 13.00]) ==  0


It's just a matter of perspective...

http://fiber-space.de/EasyExtend/doc/consoletest/consoletest.html

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Re: ten small Python programs

2007-05-28 Thread Steve Howell

--- Stef Mientki [EMAIL PROTECTED]
wrote:

 Steve Howell wrote:
  I've always thought that the best way to introduce
 new
  programmers to Python is to show them small code
  examples.  
  
 This is really a nice piece of missing Python.


Thanks.
 

 The wxPython demo program is written as an
 interactive tutorial,
 with a few hundred examples, nicely ordered in
 groups.
 The user can view the demo, the code and the help
 text.
 The user can also change the code and see the
 results right away.
 

Do you have a link?

 It would even be nicer, if everybody could drop
 her/his examples
 in a standard way, so they would be automatically
 incorporated in
 something like the wxPython interactive demo.
 

Can you elaborate?





 

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Re: ten small Python programs

2007-05-28 Thread Stef Mientki

 
 The wxPython demo program is written as an
 interactive tutorial,
 with a few hundred examples, nicely ordered in
 groups.
 The user can view the demo, the code and the help
 text.
 The user can also change the code and see the
 results right away.

 
 Do you have a link?
wxPython including demos can be downloaded from

   http://www.wxpython.org

but there's no separate page of the demo,
so I made a few screenshots:

http://oase.uci.kun.nl/~mientki/data_www/pic/jalcc/python/wxpython_overview.html

 
 It would even be nicer, if everybody could drop
 her/his examples
 in a standard way, so they would be automatically
 incorporated in
 something like the wxPython interactive demo.

 
 Can you elaborate?

Well if you see the above demo,
I've the following in mind:
- create a new-demo in a special directory
- add some special keywords in the new-demo, in which treenodes it should popup
- on restart of the demo, the new-demo is added to the tree

cheers,
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Re: ten small Python programs

2007-05-28 Thread Steve Howell

--- Stef Mientki [EMAIL PROTECTED]
wrote:
  
  It would even be nicer, if everybody could drop
  her/his examples
  in a standard way, so they would be automatically
  incorporated in
  something like the wxPython interactive demo.
 
  
  Can you elaborate?
 
 Well if you see the above demo,
 I've the following in mind:
 - create a new-demo in a special directory
 - add some special keywords in the new-demo, in
 which treenodes it should popup
 - on restart of the demo, the new-demo is added to
 the tree
 

To the extent that you just want a group of people to
be able to organically organize a tree-like collection
of Python examples, you could use a MoinMoin that has
sensible page names and the Local Site Map featured
turn on.  Are you also suggesting the need for
something local, so that you can actually run the
programs?




   
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Re: ten small Python programs

2007-05-28 Thread Stef Mientki
Steve Howell wrote:
 --- Stef Mientki [EMAIL PROTECTED]
 wrote:
 It would even be nicer, if everybody could drop
 her/his examples
 in a standard way, so they would be automatically
 incorporated in
 something like the wxPython interactive demo.

 Can you elaborate?
 Well if you see the above demo,
 I've the following in mind:
 - create a new-demo in a special directory
 - add some special keywords in the new-demo, in
 which treenodes it should popup
 - on restart of the demo, the new-demo is added to
 the tree

 
 To the extent that you just want a group of people to
 be able to organically organize a tree-like collection
 of Python examples, you could use a MoinMoin that has
 sensible page names and the Local Site Map featured
 turn on.  Are you also suggesting the need for
 something local, so that you can actually run the
 programs?

I don't know MoinMoin,
but the answer is Yes (although maybe not for your ten snippets).
First of all I think all programmers keep there own collection of code snippets,
which much more valuable then all the code code snippets from everyone.
Secondly, Python is nowadays not only used by programmers,
but also by e.g. Scientific users (former MatLab users),
who are not interested in the code itself,
but just in the results of that particular code.
For these people a lot of example programs,
for which they can easily see the results,
make some small changes and see the result again,
would be a wonderful addition.

just my 2 cents,
cheers,
Stef Mientki


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Re: ten small Python programs

2007-05-28 Thread Steve Howell

--- Stef Mientki [EMAIL PROTECTED]  

 I don't know MoinMoin,
 but the answer is Yes (although maybe not for your
 ten snippets).
 First of all I think all programmers keep there own
 collection of code snippets,
 which much more valuable then all the code code
 snippets from everyone.

Agreed.

 Secondly, Python is nowadays not only used by
 programmers,
 but also by e.g. Scientific users (former MatLab
 users),
 who are not interested in the code itself,
 but just in the results of that particular code.
 For these people a lot of example programs,
 for which they can easily see the results,
 make some small changes and see the result again,
 would be a wonderful addition.
 

In your own personal use, what are some
libraries/techniques/etc. that you think could benefit
from some kind of more organized presentation of
example programs (or better way of showing how the
examples work, etc.)?  Are you part of the Scientific
community?

How new are you to Python?  I do think
newbies/intermediates/advanceds all have different
needs.

 


   
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Re: ten small Python programs

2007-05-27 Thread Steven D'Aprano
On Sat, 26 May 2007 18:48:45 -0700, Steve Howell wrote:

 It also has a ComplexNumber class, but I don't want to
 scare away mathphobes.


Is it as short as this one-liner?

ComplexNumber = complex


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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- Steven D'Aprano
[EMAIL PROTECTED] wrote:

 On Sat, 26 May 2007 18:48:45 -0700, Steve Howell
 wrote:
 
  It also has a ComplexNumber class, but I don't
 want to
  scare away mathphobes.
 
 Is it as short as this one-liner?
 
 ComplexNumber = complex
 

The It above refers to *the* Python Tutorial,
written by Guido van Rossum.  Here is an excerpt:

 class Complex:
... def __init__(self, realpart, imagpart):
... self.r = realpart
... self.i = imagpart
... 
 x = Complex(3.0, -4.5)
 x.r, x.i
(3.0, -4.5)

Obviously, it's not surprising that a useful class in
a tutorial would have a corresponding implementation
in the standard library, but I'm not sure newbies
would learn much about classes from this statement:

ComplexNumber = complex






 

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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- Steven D'Aprano wrote:

 On Sat, 26 May 2007 18:48:45 -0700, Steve Howell
 wrote:
 
  It also has a ComplexNumber class, but I don't
 want to
  scare away mathphobes.
 
 
 Is it as short as this one-liner?
 
 ComplexNumber = complex
 

Along the idea of not reinventing a class from the
standard library in the list of ten small Python
programs (which has since grown), I went with the
classic BankAccount example for the first program to
introduce the class statement.

You can see the code here:

http://wiki.python.org/moin/SimplePrograms





   
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Re: ten small Python programs

2007-05-27 Thread BartlebyScrivener
On May 26, 1:43 pm, Steve Howell [EMAIL PROTECTED] wrote:

 --
 parentRabbits, babyRabbits = (1, 1)
 while babyRabbits  100:
 print 'This generation has %d rabbits' %
 babyRabbits
 parentRabbits, babyRabbits = (babyRabbits,
 parentRabbits + babyRabbits)

 --
 # def defines a method in Python
 def tax(itemCharge, taxRate = 0.05):
 return itemCharge * taxRate
 print '%.2f' % tax(11.35)
 print '%.2f' % tax(40.00, 0.08)


For the person new to programming (doesn't come from C or other
languages), I think you need to add a separate explanation of string
formatting and how it works, or at least add a comment that tells them
you are using string formatting so that they can search and find out
how it works. If your aim is to teach simple programming concepts, why
confuse them so early on with fancy interpolation?

Something like

# uses Python string formatting
# http://docs.python.org/lib/typesseq-strings.html

but really I think it will just be a distraction

rd


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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- BartlebyScrivener [EMAIL PROTECTED] wrote:

 On May 26, 1:43 pm, Steve Howell
 [EMAIL PROTECTED] wrote:
  --
  # def defines a method in Python
  def tax(itemCharge, taxRate = 0.05):
  return itemCharge * taxRate
  print '%.2f' % tax(11.35)
  print '%.2f' % tax(40.00, 0.08)
 
 

I decided to go with a simpler example up front.

--
# def defines a method in Python
def say_hello(name):
print 'hello', name
say_hello('Jack')
say_hello('Jill')

More here:

http://wiki.python.org/moin/SimplePrograms

Somebody also fixed a few style things in my other
examples, changing a tuple to a list, catching a more
specific exception.  Whoever you are, thanks, I agree.




   
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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- BartlebyScrivener [EMAIL PROTECTED] wrote:

 
 For the person new to programming (doesn't come from
 C or other
 languages), I think you need to add a separate
 explanation of string
 formatting and how it works, or at least add a
 comment that tells them
 you are using string formatting so that they can
 search and find out
 how it works. If your aim is to teach simple
 programming concepts, why
 confuse them so early on with fancy interpolation?
 

It's a thought provoking question, and I think my aim
here is not exactly to teach simple programming
concepts, but more to expose people to what Python
looks like.  I'm not really intending this page to be
a tutorial, as several good tutorials already exist.

I'm really targeting a particular niche of people. 
There are folks that know how to program, but don't
know anything about Python, and they really just want
to see a bunch of small examples all in one place,
without a lot of explanation cluttering their
presentation.

That may sound like I'm narrowing my audience too
much, but I do think it's a niche group that's not
adequately addressed.

I do hope, though, that folks more in a teaching role
can reuse the examples, add better explanation, etc.,
as needed.

Also, I wouldn't mind at all to add a little link
called Read more... after each example.






   
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Re: ten small Python programs

2007-05-27 Thread Wildemar Wildenburger
Steve Howell wrote:
 # def defines a method in Python
 def say_hello(name):
 print 'hello', name
 say_hello('Jack')
 say_hello('Jill')
   
Doesn't def define methods *xor* functions, depending on the context? 
And in this example, say_hello (*yuck*, underscores ...) is certainly a 
function. Or is it that functions are considered module-methods?

W
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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- Wildemar Wildenburger [EMAIL PROTECTED]
wrote:

 Steve Howell wrote:
  # def defines a method in Python
  def say_hello(name):
  print 'hello', name
  say_hello('Jack')
  say_hello('Jill')

 Doesn't def define methods *xor* functions,
 depending on the context? 
 And in this example, say_hello (*yuck*, underscores
 ...) is certainly a 
 function. Or is it that functions are considered
 module-methods?
 

Goodness, I didn't expect such a simple example to be
so controversial.  But please see the new version
here:

http://wiki.python.org/moin/SimplePrograms

I changed the method name to greet and removed the
comment, as hopefully the intent of the program will
be pretty obvious to anyone that reads it.




   
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Re: ten small Python programs

2007-05-27 Thread Steven Bethard
Steve Howell wrote:
 --- Steven Bethard [EMAIL PROTECTED] wrote:
 Very cool! Do you mind putting this up on the Wiki
 somewhere so that we 
 can link to it more easily? Maybe something like:

  http://wiki.python.org/moin/SimplePrograms

 
 Done.

I think I would rewrite the current unit-testing example to use the 
standard library unittest module::

 # Let's write reusable code, and unit test it.
 def add_money(amounts):
 # do arithmetic in pennies so as not to accumulate float errors
 pennies = sum([round(int(amount * 100)) for amount in amounts])
 return float(pennies / 100.0)
 import unittest
 class TestAddMoney(unittest.TestCase):
 def test_float_errors(self):
 self.failUnlessEqual(add_money([0.13, 0.02]), 0.15)
 self.failUnlessEqual(add_money([100.01, 99.99]), 200)
 self.failUnlessEqual(add_money([0, -13.00, 13.00]), 0)
 if __name__ == '__main__':
 unittest.main()

I believe I've still kept it to 13 lines.

STeVe

P.S. The right way to add money is using the decimal module, but I 
couldn't think of a better example.
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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- Steven Bethard [EMAIL PROTECTED] wrote:

 I think I would rewrite the current unit-testing
 example to use the 
 standard library unittest module::
 
  # Let's write reusable code, and unit test it.
  def add_money(amounts):
  # do arithmetic in pennies so as not to
 accumulate float errors
  pennies = sum([round(int(amount * 100)) for
 amount in amounts])
  return float(pennies / 100.0)
  import unittest
  class TestAddMoney(unittest.TestCase):
  def test_float_errors(self):
  self.failUnlessEqual(add_money([0.13,
 0.02]), 0.15)
  self.failUnlessEqual(add_money([100.01,
 99.99]), 200)
  self.failUnlessEqual(add_money([0,
 -13.00, 13.00]), 0)
  if __name__ == '__main__':
  unittest.main()
 
 I believe I've still kept it to 13 lines.
 

I approve this change, although in a sense, it's
harder for a Python newbie, because it introduces
inheritance a little earlier than I would have liked.

FWIW I'm in the minority (I think) of people that
prefer roll-your-own testing, but I don't want to
argue that, because I think it mostly comes down to
personal preference.

I'll only defend my position by posting this link,
which suggests that roll-your-own even has validity in
an educational setting:

http://www.elkner.net/jeff/testFirst/index.html


 P.S. The right way to add money is using the
 decimal module, but I 
 couldn't think of a better example.

Agreed.  Maybe somebody else will come up with
something more creative, but I'm happy enough with our
current version.


   
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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- Steven Bethard [EMAIL PROTECTED] wrote:
 
 I think I would rewrite the current unit-testing
 example to use the 
 standard library unittest module::
 
  # Let's write reusable code, and unit test it.
  def add_money(amounts):
  # do arithmetic in pennies so as not to
 accumulate float errors
  pennies = sum([round(int(amount * 100)) for
 amount in amounts])
  return float(pennies / 100.0)
  import unittest
  class TestAddMoney(unittest.TestCase):
  def test_float_errors(self):
  self.failUnlessEqual(add_money([0.13,
 0.02]), 0.15)
  self.failUnlessEqual(add_money([100.01,
 99.99]), 200)
  self.failUnlessEqual(add_money([0,
 -13.00, 13.00]), 0)
  if __name__ == '__main__':
  unittest.main()
 

Just a minor quibble, but wouldn't you want the import
and test class to only get executed in the ___main__
context?



   
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Re: ten small Python programs

2007-05-27 Thread Steven Bethard
Steve Howell wrote:
 --- Steven Bethard [EMAIL PROTECTED] wrote:
 I think I would rewrite the current unit-testing
 example to use the 
 standard library unittest module::

  # Let's write reusable code, and unit test it.
  def add_money(amounts):
  # do arithmetic in pennies so as not to
 accumulate float errors
  pennies = sum([round(int(amount * 100)) for
 amount in amounts])
  return float(pennies / 100.0)
  import unittest
  class TestAddMoney(unittest.TestCase):
  def test_float_errors(self):
  self.failUnlessEqual(add_money([0.13,
 0.02]), 0.15)
  self.failUnlessEqual(add_money([100.01,
 99.99]), 200)
  self.failUnlessEqual(add_money([0,
 -13.00, 13.00]), 0)
  if __name__ == '__main__':
  unittest.main()

 
 Just a minor quibble, but wouldn't you want the import
 and test class to only get executed in the ___main__
 context?

That would be fine too. In the real world, I'd put the tests in a 
different module.

STeVe
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Re: ten small Python programs

2007-05-27 Thread Steven Bethard
Steve Howell wrote:
 --- Steven Bethard [EMAIL PROTECTED] wrote:
 
 I think I would rewrite the current unit-testing
 example to use the 
 standard library unittest module::

  # Let's write reusable code, and unit test it.
  def add_money(amounts):
  # do arithmetic in pennies so as not to
 accumulate float errors
  pennies = sum([round(int(amount * 100)) for
 amount in amounts])
  return float(pennies / 100.0)
  import unittest
  class TestAddMoney(unittest.TestCase):
  def test_float_errors(self):
  self.failUnlessEqual(add_money([0.13,
 0.02]), 0.15)
  self.failUnlessEqual(add_money([100.01,
 99.99]), 200)
  self.failUnlessEqual(add_money([0,
 -13.00, 13.00]), 0)
  if __name__ == '__main__':
  unittest.main()

 I believe I've still kept it to 13 lines.

 
 I approve this change, although in a sense, it's
 harder for a Python newbie, because it introduces
 inheritance a little earlier than I would have liked.
 
 FWIW I'm in the minority (I think) of people that
 prefer roll-your-own testing, but I don't want to
 argue that, because I think it mostly comes down to
 personal preference.

Have you tried py.test?

 http://codespeak.net/py/dist/test.html

I've heard good things about it, but haven't gotten around to trying it 
yet. Here's a two-line test suite from the page above:

 def test_answer():
 assert 42 == 43

STeVe
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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- Steven Bethard [EMAIL PROTECTED] wrote:

 Steve Howell wrote:
  --- Steven Bethard [EMAIL PROTECTED]
 wrote:
  I think I would rewrite the current unit-testing
  example to use the 
  standard library unittest module::
 
   # Let's write reusable code, and unit test
 it.
   def add_money(amounts):
   # do arithmetic in pennies so as not to
  accumulate float errors
   pennies = sum([round(int(amount * 100))
 for
  amount in amounts])
   return float(pennies / 100.0)
   import unittest
   class TestAddMoney(unittest.TestCase):
   def test_float_errors(self):
  
 self.failUnlessEqual(add_money([0.13,
  0.02]), 0.15)
  
 self.failUnlessEqual(add_money([100.01,
  99.99]), 200)
   self.failUnlessEqual(add_money([0,
  -13.00, 13.00]), 0)
   if __name__ == '__main__':
   unittest.main()
 
  
  Just a minor quibble, but wouldn't you want the
 import
  and test class to only get executed in the
 ___main__
  context?
 
 That would be fine too. In the real world, I'd put
 the tests in a 
 different module.
 

Maybe this is the first good example that motivates a
hyperlink to alternatives.  Would you accept the idea
that we keep my original example on the SimplePrograms
page, but we link to a UnitTestingPhilosophies page,
and we show your alternative there?  Or vice versa,
show your example on the first page, but then show
mine on the hyperlinked page?

I am in 100% agreement with you that most unit tests
would be completely outside the module, although I
often follow the practice that my modules have a
little if __main__ section that runs a few simple
unit tests, as sort of a bit of self-documentation.




   
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Re: ten small Python programs

2007-05-27 Thread Steven Bethard
Steve Howell wrote:
 --- Steven Bethard [EMAIL PROTECTED] wrote:
 
 Steve Howell wrote:
 --- Steven Bethard [EMAIL PROTECTED]
 wrote:
 I think I would rewrite the current unit-testing
 example to use the 
 standard library unittest module::

  # Let's write reusable code, and unit test
 it.
  def add_money(amounts):
  # do arithmetic in pennies so as not to
 accumulate float errors
  pennies = sum([round(int(amount * 100))
 for
 amount in amounts])
  return float(pennies / 100.0)
  import unittest
  class TestAddMoney(unittest.TestCase):
  def test_float_errors(self):
 
 self.failUnlessEqual(add_money([0.13,
 0.02]), 0.15)
 
 self.failUnlessEqual(add_money([100.01,
 99.99]), 200)
  self.failUnlessEqual(add_money([0,
 -13.00, 13.00]), 0)
  if __name__ == '__main__':
  unittest.main()

 Just a minor quibble, but wouldn't you want the
 import
 and test class to only get executed in the
 ___main__
 context?
 That would be fine too. In the real world, I'd put
 the tests in a 
 different module.

 
 Maybe this is the first good example that motivates a
 hyperlink to alternatives.  Would you accept the idea
 that we keep my original example on the SimplePrograms
 page, but we link to a UnitTestingPhilosophies page,
 and we show your alternative there?  Or vice versa,
 show your example on the first page, but then show
 mine on the hyperlinked page?

Sure.  Either way is fine.

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Re: ten small Python programs

2007-05-27 Thread Steve Howell

--- Steven Bethard [EMAIL PROTECTED] wrote:
  
  Maybe this is the first good example that
 motivates a
  hyperlink to alternatives.  Would you accept the
 idea
  that we keep my original example on the
 SimplePrograms
  page, but we link to a UnitTestingPhilosophies
 page,
  and we show your alternative there?  Or vice
 versa,
  show your example on the first page, but then show
  mine on the hyperlinked page?
 
 Sure.  Either way is fine.
 

Ok, for now, I'm taking no action, let's let the unit
testing discussion progress a little.  Despite my
saying early that I don't want to debate it, I do want
to discuss it :), as it is near in dear to my heart.



   
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Re: ten small Python programs

2007-05-27 Thread Paul Rubin
Steven Bethard [EMAIL PROTECTED] writes:
 I think I would rewrite the current unit-testing example to use the
 standard library unittest module::

I think these days we're supposed to like doctest better than unittest.
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Re: ten small Python programs

2007-05-27 Thread Adonis Vargas
Steve Howell wrote:
 I've always thought that the best way to introduce new
 programmers to Python is to show them small code
 examples.  

snip

You could try this wiki page:

http://rosettacode.org/wiki/Main_Page

It has a fair amount of Python examples as well as many more other 
languages (doing the same algorithm).

Hope this helps.

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Re: ten small Python programs

2007-05-27 Thread DJ Fadereu


 You could try this wiki page:

 http://rosettacode.org/wiki/Main_Page

 It has a fair amount of Python examples as well as many more other
 languages (doing the same algorithm).

 Hope this helps.

 Adonis


THIS IS GREAT :) Thanx!

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Re: ten small Python programs

2007-05-26 Thread John K Masters
On 11:43 Sat 26 May , Steve Howell wrote:
 I've always thought that the best way to introduce new
 programmers to Python is to show them small code
 examples.  
 
 When you go to the tutorial, though, you have to wade
 through quite a bit of English before seeing any
 Python examples.
 
 Below is my attempt at generating ten fairly simple,
 representative Python programs that expose new users
 to most basic concepts, as well as the overall syntax.
 
 It was an interesting exercise.  I constrained myself
 to ten lines or less, and it was pretty easy to
 incorporate loops, conditionals, print, open(), lists,
 tuples, dictionaries, and imported modules.  
 
 It was harder to show classes, and my ShoppingCart
 class is nothing more than an encapsulation of a list,
 which has dubious value (although it's the start of
 something more useful).
 
 Anyway, here goes:
 

Many thanks for that. This is exactly what is missing in most introductory
books. Simple, relevant and concise examples.

Regards, John
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Re: ten small Python programs

2007-05-26 Thread Steven Bethard
Steve Howell wrote:
 I've always thought that the best way to introduce new
 programmers to Python is to show them small code
 examples.  
 
 When you go to the tutorial, though, you have to wade
 through quite a bit of English before seeing any
 Python examples.
 
 Below is my attempt at generating ten fairly simple,
 representative Python programs that expose new users
 to most basic concepts, as well as the overall syntax.


Very cool! Do you mind putting this up on the Wiki somewhere so that we 
can link to it more easily? Maybe something like:

 http://wiki.python.org/moin/SimplePrograms

nitpick
Though the code should probably follow PEP 8 guidelines, e.g. 
under_scores instead of camelCase for object and method names:

 http://www.python.org/dev/peps/pep-0008/
/nitpick

 class ShoppingCart:
 def __init__(self): self.items = []
 def buy(self, item): self.items.append(item)
 def boughtItems(self): return self.items
 myCart = ShoppingCart()
 myCart.buy('apple')
 myCart.buy('banana')
 print myCart.boughtItems()

I think boughtItems() is probably not a good example of Python code 
since in this case, you should probably just write ``my_cart.items``. 
Maybe it should define ``__len__`` instead? Or maybe something like::

 def select_items(self, prefix):
 return [item for item in self.items if item.startswith(prefix)]


STeVe
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Re: ten small Python programs

2007-05-26 Thread Steve Howell

--- Steven Bethard [EMAIL PROTECTED] wrote:
 Very cool! Do you mind putting this up on the Wiki
 somewhere so that we 
 can link to it more easily? Maybe something like:
 
  http://wiki.python.org/moin/SimplePrograms


Done.
 
 nitpick
 Though the code should probably follow PEP 8
 guidelines, e.g. 
 under_scores instead of camelCase for object and
 method names:
 
  http://www.python.org/dev/peps/pep-0008/
 /nitpick
 

I think I fixed them, please see Wiki to verify.


  class ShoppingCart:
  def __init__(self): self.items = []
  def buy(self, item):
 self.items.append(item)
  def boughtItems(self): return self.items
  myCart = ShoppingCart()
  myCart.buy('apple')
  myCart.buy('banana')
  print myCart.boughtItems()
 
 I think boughtItems() is probably not a good example
 of Python code 
 since in this case, you should probably just write
 ``my_cart.items``. 
 Maybe it should define ``__len__`` instead? Or maybe
 something like::
 
  def select_items(self, prefix):
  return [item for item in self.items if
 item.startswith(prefix)]
 

I think the problem here is that it's hard to write a
useful class in less than 10 lines of code.  Can
somebody else give it a try?

Although I didn't call it out in the email, I tried to
make each program progressively one line longer, so if
somebody wants to write, say, an 11-line class
example, then I will try fill in the gap with another
8-liner.

Did I miss any basic concepts in the first 10
programs?  Maybe an 8-liner could demonstrate command
line arguments?






   
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Re: ten small Python programs

2007-05-26 Thread Paul McGuire
I ***love*** this 10 Little Programs idea!  As soon as I get a
breathing space, I'm going to add a 10 Little Parsers page to the
pyparsing wiki!

On May 26, 2:38 pm, Steven Bethard [EMAIL PROTECTED] wrote:
 nitpick
 Though the code should probably follow PEP 8 guidelines, e.g.
 under_scores instead of camelCase for object and method names:

  http://www.python.org/dev/peps/pep-0008/
 /nitpick

Really?  Underscore-separated words preferred over camel case?  What
is the rationale for this?  This style is so retro/80's/C-ish.  It
seems more like a Java backlash to me than anything else.  If we (or
Guido) don't like changing case to indicate word breaks, why are class
names to be UpperCamelCase, and not Capitalized_with_underscores?  If
there is a casing convention nit to pick, I'd focus on UpperCamelCase
for class names, lower case (either with underscores or mixed case)
for attributes and method names, and UNDERSCORE_SEPARATED_ALL_CAPS for
constants.

If we want to just say well, PEP-8 says such and such, I think this
is an area where the thinking has possibly evolved since 2001.  Also,
I think the PEP would benefit from explicitly discouraging some
practices, such as Hungarian notation.


  class ShoppingCart:
  def __init__(self): self.items = []
  def buy(self, item): self.items.append(item)
  def boughtItems(self): return self.items
  myCart = ShoppingCart()
  myCart.buy('apple')
  myCart.buy('banana')
  print myCart.boughtItems()

If you want to nitpick, I'd rather go after the one-liner methods with
the body on the same line as the def statement.

How's this for a better non-trivial method example:

MAX_ITEMS_FOR_EXPRESS_LANE = 10
def canUseExpressLane(self):
return (len(self.items) = MAX_ITEMS_FOR_EXPRESS_LANE)

or call it can_use_express_lane if you must.

I guess pyparsing with its mixedCase functions and attributes is
doomed for the Dunce Corner.  Too bad for BeautifulSoup, cElementTree,
and wxPython that are also at variance with this canon of Python
coding style. (Modules should have short, all-lowercase names. ...
Python packages should also have short, all-lowercase names, although
the use of underscores is discouraged.)

-- Paul

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Re: ten small Python programs

2007-05-26 Thread Steve Holden
Paul McGuire wrote:
[...].
 
 I guess pyparsing with its mixedCase functions and attributes is
 doomed for the Dunce Corner.  Too bad for BeautifulSoup, cElementTree,
 and wxPython that are also at variance with this canon of Python
 coding style. (Modules should have short, all-lowercase names. ...
 Python packages should also have short, all-lowercase names, although
 the use of underscores is discouraged.)
 
Although the names in wxPython are indeed contrary to PEP 8 (because 
they are the same as the names used in wxWidgets) I should point out 
that nowadays the name you import is wx.

regards
  Steve
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Re: ten small Python programs

2007-05-26 Thread Steve Howell

--- Paul McGuire [EMAIL PROTECTED] wrote:

 I ***love*** this 10 Little Programs idea!  As
 soon as I get a
 breathing space, I'm going to add a 10 Little
 Parsers page to the
 pyparsing wiki!


Thanks. :)

I'm thinking you could actually have a progression
from a 1 line program up to a 50-line program.  The
number 50 is kind of arbitrary, but my gut says that
by a 50-line program, you will have demonstrated
almost every useful concept.

 
 
 
   class ShoppingCart:
   def __init__(self): self.items = []
   def buy(self, item):
 self.items.append(item)
   def boughtItems(self): return self.items
   myCart = ShoppingCart()
   myCart.buy('apple')
   myCart.buy('banana')
   print myCart.boughtItems()
 
 If you want to nitpick, I'd rather go after the
 one-liner methods with
 the body on the same line as the def statement.
 

Agreed.  I didn't like that either.

 How's this for a better non-trivial method example:
 
 MAX_ITEMS_FOR_EXPRESS_LANE = 10
 def canUseExpressLane(self):
 return (len(self.items) =
 MAX_ITEMS_FOR_EXPRESS_LANE)
 
 or call it can_use_express_lane if you must.
 

Yep, that sounds more in the ballpark of what I'd want
to show, versus a weakish class that just encapulates
a list.

Here's my challenge to whoever wants to take it--write
(or find) a program with 20 or fewer lines that
sufficiently motivates the need for classes, has
decent Python style, and is newbie friendly.

The tutorial has this example, which is useful for
demonstrating the syntax of classes, but it doesn't
actually do anything interesting:

class MyClass:
A simple example class
i = 12345
def f(self):
return 'hello world'

It also has a ComplexNumber class, but I don't want to
scare away mathphobes.

It does have this idiom, which I think is worth
putting somewhere into the progression.

class Employee:
pass

john = Employee() # Create an empty employee record

# Fill the fields of the record
john.name = 'John Doe'
john.dept = 'computer lab'
john.salary = 1000





   
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Re: ten small Python programs

2007-05-26 Thread Paul McGuire
On May 26, 8:48 pm, Steve Howell [EMAIL PROTECTED] wrote:

 I'm thinking you could actually have a progression
 from a 1 line program up to a 50-line program.  The
 number 50 is kind of arbitrary, but my gut says that
 by a 50-line program, you will have demonstrated
 almost every useful concept.


If there is anything arbitrary here, I'd say it is your increment
each example by one source line constraint.  This can force you to
use some bad coding practices to meet your target line count for a
given example.

Maybe try this approach:  pick your top 10/20/50 language features and
develop concise examples. Then order the examples by length as a first
cut (longer examples probably *are* more complex), and then reorder a
bit to handle pre-requisites (introduce a minimum of new features,
preferably 1, per example).  Overall, I'd have a tough time picking
just 10 language features to illustrate, but there are probably 10-20
basic features that will get new people onto fairly productive
ground.  Pick 20 as your example count (50 sounds a bit long), and
stick to it, and then later add 20 More Little Programs for the next
wave of examples in increasing complexity.

One other nit to pick: have your example classes inherit from object,
to get new people using new-style classes from the get-go.

-- Paul

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Re: ten small Python programs

2007-05-26 Thread Steven Bethard
Paul McGuire wrote:
 I ***love*** this 10 Little Programs idea!  As soon as I get a
 breathing space, I'm going to add a 10 Little Parsers page to the
 pyparsing wiki!
 
 On May 26, 2:38 pm, Steven Bethard [EMAIL PROTECTED] wrote:
 nitpick
 Though the code should probably follow PEP 8 guidelines, e.g.
 under_scores instead of camelCase for object and method names:

  http://www.python.org/dev/peps/pep-0008/
 /nitpick
 
 Really?  Underscore-separated words preferred over camel case?  What
 is the rationale for this?

Rationale?  It's a style guide.  There is no rationale. ;-)

 If we want to just say well, PEP-8 says such and such, I think this
 is an area where the thinking has possibly evolved since 2001.

I really don't think so. If anything, it's gotten more strict. PEP 8 
used to allow either camelCase or under_scores. Now it only allows the 
latter.

 I guess pyparsing with its mixedCase functions and attributes is
 doomed for the Dunce Corner.  Too bad for BeautifulSoup, cElementTree,
 and wxPython that are also at variance with this canon of Python
 coding style.

Many (if not all) of these modules were written before the most recent 
incarnation of PEP 8. Thus, they fall under the second good reason to 
break a particular rule:

 (2) To be consistent with surrounding code that also breaks it

Of course, for new code, such as that in this thread, there's no reason 
to break from the PEP 8 guidelines.


STeVe
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Re: ten small Python programs

2007-05-26 Thread Steve Howell

--- Paul McGuire [EMAIL PROTECTED] wrote:

 On May 26, 8:48 pm, Steve Howell
 [EMAIL PROTECTED] wrote:
 
  I'm thinking you could actually have a progression
  from a 1 line program up to a 50-line program. 
 The
  number 50 is kind of arbitrary, but my gut says
 that
  by a 50-line program, you will have demonstrated
  almost every useful concept.
 
 
 If there is anything arbitrary here, I'd say it is
 your increment
 each example by one source line constraint.  This
 can force you to
 use some bad coding practices to meet your target
 line count for a
 given example.


I understand your point, but I'm sticking to the
concept for now.  My intent with the progression isn't
so much for each example to thoroughly teach a concept
(although I could certainly hyperlink to a more
in-depth treatment), but really more to give a bird's
eye view of the language very quickly.

I recently helped teach a Java programmer to program
in Python, and he learned a lot just by seeing simple
examples.  So I guess my target audience isn't so much
people learning how to program; it's more for
programmers getting their first exposure to Python.

On the other side of the fence, I recently tried to
relearn a bit of Ruby, and I remember being frustrated
by their tutorials, as really, I just wanted to see a
bunch of simple programs, and I can figure out mostly
what they're doing.  Instead, I had to wade through
verbose descriptions of what a variable is, rules for
how you construct identifiers, etc.
 
 Maybe try this approach:  pick your top 10/20/50
 language features and
 develop concise examples. Then order the examples by
 length as a first
 cut (longer examples probably *are* more complex),
 and then reorder a
 bit to handle pre-requisites (introduce a minimum of
 new features,
 preferably 1, per example).  Overall, I'd have a
 tough time picking
 just 10 language features to illustrate, but there
 are probably 10-20
 basic features that will get new people onto fairly
 productive
 ground.  Pick 20 as your example count (50 sounds a
 bit long), and
 stick to it, and then later add 20 More Little
 Programs for the next
 wave of examples in increasing complexity.
 

My only reluctance with that approach is that it
sounds like a little more work than I'm ready to take
on right away.  But it's on the Wiki now, so maybe
other folks can help me grow it.

 One other nit to pick: have your example classes
 inherit from object,
 to get new people using new-style classes from the
 get-go.
 

My only fear here is that when old classes go away
(Py3K? I don't know), that practice may become
obsolete.

But on a more general note, I welcome folks to just
clean up my examples on the Wiki if I accidentally
introduce some bad practices...but preserving line
counts. :)





 

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Re: ten small Python programs

2007-05-26 Thread Paul McGuire
Out of curiosity, how does this style jibe with the latest embracing
of Unicode identifiers?  Ever tried to type an underscore on a non-US
keyboard?  I have a heck of a time finding/typing the '_' character
when I visit our clients in Germany, but this may just be my own
personal Amerocentric issue (I also get messed up by the transposition
of Y and Z on German keyboards, but my German colleagues
understandably are not bothered by it).  For someone already familiar
with that keyboard layout, is typing an underscore any more difficult
than my pressing Shift-_ on my US keyboard?

-- Paul

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Re: ten small Python programs

2007-05-26 Thread Paul McGuire
On May 26, 9:58 pm, Paul McGuire [EMAIL PROTECTED] wrote:
 Out of curiosity, how does this style jibe with the latest embracing
 of Unicode identifiers?  Ever tried to type an underscore on a non-US
 keyboard?  I have a heck of a time finding/typing the '_' character
 when I visit our clients in Germany, but this may just be my own
 personal Amerocentric issue (I also get messed up by the transposition
 of Y and Z on German keyboards, but my German colleagues
 understandably are not bothered by it).  For someone already familiar
 with that keyboard layout, is typing an underscore any more difficult
 than my pressing Shift-_ on my US keyboard?

 -- Paul

Steve, sorry for going so far off-topic.  I've started a new thread on
my questions about this aspect of PEP-8, and if there's more to say
about this, people should post it there.

-- Paul

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