Lists in classes
wildemar at freakmail.de
Thu Jul 12 17:51:58 CEST 2007
Bart Ogryczak wrote:
> On 12 jul, 17:23, Jeremy Lynch <jeremy.ly... at gmail.com> wrote:
>> Learning python from a c++ background. Very confused about this:
>> class jeremy:
> You've defined list (very bad choice of a name, BTW), as a class
> variable. To declare is as instance variable you have to prepend it
> with "self."
'self' is *not* a reserved ord in python, it doesn't do anything. So
just popping 'self' in front of something doesn't bind it to an instance.
Here is how it works:
class Jeremy(object): # you better inherit from 'object' at all times
classlist =  # class variable
def __init__(self): # "constructor"
self.instancelist =  # instance variable
def add_item(self, item):
'self' is the customary name for the first argument of any instance
method, which is always implicitly passed when you call it. I think it
translates to C++'s 'this' keyword, but I may be wrong. Simply put: The
first argument in an instance-method definition (be it called 'self' or
otherwise) refers to the current instance.
Note however that you don't explicitly pass the instance to the method,
that is done automatically:
j = Jeremy() # Jeremy.__init__ is called at this moment, btw
j.add_item("hi") # See? 'item' is the first arg you actually pass
I found this a bit confusing at first, too, but it's actually very
clean, I think.
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