A classical example is a class that can be constructed from different values.
Ok, let's implement a special integer class:
class MyOwnInteger(object):
def __init__(self, value):
self.value = value
Now, let's say we want to add the possibility to create MyOwnInteger
instances from strings. We can accomplish this by checking the type of
value inside of __init__, but this does not scale if there might be
different interpretations for a string:
class MyOwnInteger(object):
def __init__(self, value):
self.value = value
@classmethod
def fromString(cls, value):
return cls(int(value))
@classmethod
def fromFiledata(cls, filename):
fp = file(filename)
data = fp.read()
fp.close()
return cls(int(data.strip()))
Andreas
Am Sonntag, den 23.03.2008, 16:11 -0700 schrieb Tony Cappellini:
> Kent
>
> Would you show the examples which show where staticmethod &
> classmethod are used?
>
> I've often wondered about the usefulness of these myself. Having read
> many of the popular books on python, none provide a good clear
> explanation
> of why or where these should be used, and what the alternatives are
> (if any). They typically show an extremely terse example of the syntax
> with little explanation.
>
>
> Message: 7
> Date: Sun, 23 Mar 2008 18:26:26 -0400
> From: Kent Johnson <[EMAIL PROTECTED]>
> Subject: Re: [Tutor] what is @classmethod and @staticmethod ??
> To: maser <[EMAIL PROTECTED]>
> Cc: tutor@python.org
> Message-ID: <[EMAIL PROTECTED]>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> maser wrote:
> > Thanks, Andreas. Why do we need to use classmethod/
> > staticmethod and where do we need to use them ?
>
> I use staticmethods as a convenience to put related functions in the
> namespace of a class. Perhaps foo.py contains class Foo with
> staticmethod bar(). In client code I can say
>
> from foo import Foo
> Foo.bar()
>
> If bar was a module method it would be
>
> from foo import Foo, bar
> bar()
>
>
> I prefer the former in cases where bar is related to Foo.
>
> Kent
> _______________________________________________
> Tutor maillist - Tutor@python.org
> http://mail.python.org/mailman/listinfo/tutor
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