Instance method as function object

Question

I need to pass an instance method as an argument to a function:

class C(object):
    def m(self):
        print("m",self)

def f(l,b):
    for z in l:
        b(z)

x = C()

f([x], lambda c: c.m())

is there a better way than the lambda?

It appears that f([x], C.m) works too, but is this an accident or an official feature?

C.m will be a reference to an unbound method (as in no associated self instance). Passing <instance>.m would work though. — jedwards
– jedwards, Commented Jun 10, 2018 at 4:44

John Zwinck · Accepted Answer · 2018-06-10 04:50:23Z

2

You can do this:

f([x], C.m)

Here, C.m is the method without an instance. It does the same thing as your lambda. It is definitely an official and supported feature.

answered Jun 10, 2018 at 4:50

John Zwinck

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Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

>>> from operator import methodcaller
>>> f([x], methodcaller('m'))
m <__main__.C object at 0x1317bbda0>

methodcaller returns a callable that will call a method on a given instance passed to it.

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answered Jun 10, 2018 at 4:50

cs95

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