[Baypiggies] Discussion for newbies/beginner night talks

[Shannon -jj Behrens]

#) Unlike a lot of languages, Python has a nice *mix* of the
programming paradigms.  It's not just OO.  You should embrace this.
Let me run down the list with some examples:

Procedural:

Code everything in functions.  You can put functions inside of
functions and lexical scoping works like in Pascal.

Functional:

>>> l = [1, 2, 3, None, 1.2]
>>> filter(None, l)
[1, 2, 3, 1.2]
>>> l = [1, 2, 3]
>>> filter(lambda x: x > 2, l)
[3]
>>> map(str, l)
['1', '2', '3']

>>> # A closure.
>>> def greeter(name):
...     def greet():
...         print "Hello, my name is %s" % name
...     return greet
...
>>> greet = greeter('JJ')
>>> greet()
Hello, my name is JJ
>>> # Now I can pass my special greet somewhere else.

Modern functional programming a la Haskell:

>>> l = [1, 2, 3, None, 1.2]
>>> [i for i in l if l is not None]
[1, 2, 3, None, 1.2]
>>> l = [1, 2, 3]
>>> [i for i in l if i > 2]
[3]
>>> [str(i) for i in l]
['1', '2', '3']

Object oriented:

>>> class Fruit:
...     def good_for_you(self):
...         return True
...
>>> class Orange(Fruit):
...     def taste(self):
...         return "sweet"
...
>>> class Lemon(Fruit):
...     def taste(self):
...         return "sour"
...
>>> fruit = [Orange(), Lemon()]
>>> for i in fruit:
...     print i.__class__.__name__
...     print i.good_for_you()
...     print i.taste()
...
Orange
True
sweet
Lemon
True
sour

But unlike Java, we have bound methods:

>>> taste = Orange().taste
>>> # I can now pass taste around as a function pointer.
...
>>> taste()
'sweet'

Imperative:

a = 0
a += 1  # That's a functional programming joke ;)

Aspect oriented programming:

>>> # Functions:
...
>>> def sum(a, b):
...     print a + b
...
>>> # Aspects:
...
>>> def wrap_function(f):
...     def inner(*args, **kargs):
...         print "Calling %s with %r %r" % (
...             f.func_name, args, kargs)
...         return f(*args, **kargs)
...     return inner
...
>>> # Weave them together:
...
>>> sum = wrap_function(sum)
>>>
>>> # Test:
...
>>> sum(1, 2)
Calling sum with (1, 2) {}
3

Logic-based:

Here's a Python-take on Prolog:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/303057

Ok, I'm out of paradigms ;)

Happy Hacking!
-jj