On 14/09/06, Chris Hengge <[EMAIL PROTECTED]> wrote:
> Can anyone explain what I've been reading? I'm trying to understand why
> many documents show:
> def myMethod(vars):
> or
> class myClass(var):
> and others show:
> def myMetheod(self, vars)
> or
> class myClass(self, vars)
Um. Can you give an example of something saying "class myClass(self,
vars)" ? The "arguments" to a class are other classes that you want
to inherit from, and are different from function arguments!
As to your other question, though ---
Suppose I have a class:
class MyClass(object):
# etc
And suppose I create an instance of that class:
mc = MyClass()
And then I call a method on that instance:
mc.someFunc(3, 'foo')
Although I have given the function someFunc two arguments, it will
actually be passed _three_ arguments. The first argument will be mc
itself. So, in the definition of MyClass, you would have:
def someFunc(self, x, s):
# etc
"self" is the name traditionally given to the first parameter, which
receives the class instance. If you wanted to make things explicit,
you could instead do:
MyClass.someFunc(mc, 3, 'foo')
I think this is exactly equivalent to mc.someFunc(3, 'foo'). (someone confirm?)
On the other hand, if you're writing a utility function that's not
part of a class, you won't give it a "self" parameter.
Hope this helps :-)
> Also, what is with the double underscores? (__init__ for example) is
> this required? or a Pythonic naming convention? When and how to use?
Various special methods have the form "__xxx__". For example, the
builtin function str converts things into strings. str is associated
with the special method __str__. If you write:
s = str(o)
this is equivalent to:
s = o.__str__()
and you can define / override the __str__ function in your own classes
to control how they are converted to strings.
Also, there is a convention that variable names starting with a single
underscore are private (since there's no "true" concept of
private/public in python). Variable names starting with two
underscores are "more private", and python mangles the name a bit.
eg, try the following:
class Foo(object):
def __init__(self):
self.x = 1
self._y = 2
self.__z = 3
f = Foo()
print f.x
print f._y
print f.__z
> I'm 'trying' to write clear pythonic code since in all reality it gives
> a nice polish to the code when compared to writing c style.
I don't think you'll find many here who disagree with that :-)
--
John.
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