My python annoyances so far

[Neil Cerutti]

On 2007-04-26, Steven Howe <howe.steven at gmail.com> wrote:
> flifus at gmail.com wrote:
>>> Well, why do some things in the library have to be functions,
>>> and other things have to be class methods?
>
> Perhaps because some things are more naturally function like?
> For 'instance' (pardon the pun), functions shouldn't retain
> data. They perform an operation, return data and quit. While
> retaining data is a feature of an class/instance.

Functions do retain data. Classes and instances are just a
convenient notation. ;)

>>> def funmaker(f, x):
...   return lambda: f(x)
...
>>> d = funmaker(int, 10)
>>> d()
10

In addition, all functions in Python have data members, too.

>>> d.label = "d"
>>> d.label
'd'

Python's scoping rules make certain kinds of functional idioms
hard to use, though. I'm not sure how to get the following to
work in Python using functions:

>>> def account(s):
...   b = s
...   def add(a):
...     b += a
...   def balance():
...     return b
...   return add, balance
...
>>> add, balance = account(100)
>>> balance()
100
>>> add(5)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<stdin>", line 4, in add
UnboundLocalError: local variable 'b' referenced before assignment

Anyhow, it doesn't work, but you can see how closely it resembles
a class definition.

> And before someone get's all technical, I know everything in
> Python is an 'object' even None, which implies class, or is it
> the other way around?

Classes are just objects like everything else.

-- 
Neil Cerutti
Bach's death is attributed to the end of the Baroque era. --Music Lit Essay