On Sun, Jan 1, 2012 at 8:40 PM, Stayvoid <stayv...@gmail.com> wrote: > Hi there! > >>>> class Sample: >>>> def method(self): pass > >>>> Sample().method() > > What's the difference between class __main__.Sample and > __main__.Sample instance? > Why should I write "Sample().method" instead of "Sample.method"? >
The difference can be illustrated as such: >>> Sample().method <bound method Sample.method of <__main__.Sample instance at 0x1004d1638>> >>> Sample().method() >>> Sample.method <unbound method Sample.method> >>> Sample.method() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unbound method method() must be called with Sample instance as first argument (got nothing instead) >>> That is, the difference between the methods is that the accessed through the instance is also attached to that instance. It will automagically get Sample() passed to it as its first argument (that would be self). The one attached to the class is unbound, which means that you can do this: >>> Sample.method(Sample()) >>> With any Sample instance, of course. This exposes a bit of syntax sugar in python and how classes are really implemented, essentially the fact that, if "a" is a sample instance, a.method(arg1, arg2, arg3) is actually just Sample.method(a, arg1, arg2, arg3) HTH, Hugo _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
