importing a method
bignose+hates-spam at benfinney.id.au
Mon Nov 28 01:25:15 CET 2005
Flavio <fccoelho at gmail.com> wrote:
> Class soandso:
> def __init__(self):
> self.this = 0
> self.that = 1
> def meth1(self):
> def meth2(self):
> def custom(self):
> I want to allow the user to write a python module that declares a
> function so that myprogram can import it and attribute it to the custom
> method of the soandso object. So far so good, that is an easy thing to
> do in Python.
> import usermodule
> a.custom = usermodule.function
Apparently you haven't tested whether this works. It doesn't:
>>> class Foo(object):
>>> def bar(*args):
... print "bar() got arguments:", args
>>> bar("spam", "eggs")
bar() got arguments: ('spam', 'eggs')
>>> Foo.bar_method = bar
>>> Foo.bar_method("spam", "eggs")
Traceback (most recent call last):
File "<stdin>", line 1, in ?
TypeError: unbound method bar() must be called with Foo instance as first argument (got str instance instead)
> But, what if the method had to access the self attributes (self.this
> and self.that) of the soandso object?
To become a method, the function must be bound to an instance, and the
method will then receive the instance as the first argument when
called as a method.
To do this on an already-defined function, use new.instancemethod.
>>> import new
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