Binding a method to class instance on fly in Python

Question

class mc:
    def show(self):
        self.func()


a = mc()
def myfunc(self):
    print('instance function')
a.func = myfunc
a.show()

The above does not work: TypeError: myfunc() missing 1 required positional argument: 'self'.

Why is the instance name not automatically inserted by Python, considering that I'm using dot notation?

If you want to make an instance method, just make it an instance method in the regular way. However for your myfunc I would expect it to be a regular function that you are just storing as the func attrbute of a particuar instance of mc. — Andrew Allaire
– Andrew Allaire, Commented Feb 15, 2022 at 6:38

BrokenBenchmark · Accepted Answer · 2022-02-15 06:41:26Z

1

You can dynamically add a method to a class using monkey patching.

class mc:
    def show(self):
        self.func()

a = mc()
def myfunc(self):
    print('instance function')
mc.func = myfunc
a.show()

answered Feb 15, 2022 at 6:41

BrokenBenchmark

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Comments

Mohamed ElKalioby · Accepted Answer · 2022-02-15 06:39:01Z

1

It can work like this, since the function isn't really an instance method

class mc:
    def show(self):
         self.x = 1
         func(self)


a = mc()
def myfunc(self):
    print (self.x)
    print('instance function')
a.func = myfunc
a.show()

answered Feb 15, 2022 at 6:39

Mohamed ElKalioby

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