Python pass function name as argument

Question

My goal is to write a class that should allow me to determine which method to call ( A1 or A2 ) while creating an object p. C will call B, B will call A.

def A1():
    return 'A1_g'
def A2():
    return 'A2_g'

class test:

    def __init__(self, means=None):
        self.means=means

    def A1(self):
        return 'A1'
    def A2(self):
        return 'A2'
    def B(self,A):
        new_string='methodB called '+A()
        print new_string
    def C(self):
        q=self.B(self.means)
        return q

p=test(means=A1)

p.C()

I got this output "methodB called A1_g". But I want "methodB called A1"

If I delete the top 2 fn definition, I got "NameError: name 'A1' is not defined". Want to understand how and why to achieve this.

I am looking for a way to modify method B inside the class, in order to make object p convenience to use? Such as just pass the name of fn A1 (or through a string) to call A or modify A1 name leading/trailing with some __? I have many fn name to pass in. I had read How do I pass a method as a parameter in python and Python: pass method as argument in function before this post, but not get an direct answer. — Yang
– Yang, Commented Nov 19, 2015 at 15:20
I updated my answer with a way to pass the name of A1 as a string. — John1024
– John1024, Commented Nov 19, 2015 at 22:04

John1024 · Accepted Answer · 2015-11-19 22:03:29Z

3

>>> p = test(means=test().A1)
>>> p.C()
methodB called A1

Or, more concisely:

>>> test(means=test().A1).C()
methodB called A1

Alternative: passing the method name as a string

If, instead of passing the method itself, we want to pass the name of the method as a string, then we need to change method B as follows:

    def B(self,A):
        method = getattr(self, A)
        new_string='methodB called ' + method()
        print new_string

The getattr function returns the attribute of self that is named by the variable A.

Now, this can be run as follows:

>>> p = test(means="A1")
>>> p.C()
methodB called A1

edited Nov 19, 2015 at 22:03

answered Nov 19, 2015 at 4:26

John1024

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