Nested classes in object oriented python

Question

I would like to do the following:

import mymodule

m = mymodule.MyModule()

m.dosth()
# Does something

m.more.domore()
# Does more

The mymodule __init__.py file looks like this:

class MyModule():
    def __init__(self):
        pass # Constructor

    def dosth(self):
        print("My module is doing something!")
    
    class more:
        def domore(self):
            print("My module is doing even more!")

But when I run my script, a TypeError occurres: TypeError: domore() missing 1 required positional argument: 'self. How can I call methods from the class more without getting errors?

Why? Nested classes are rare in Python, as are static methods (though less so). — chepner
– chepner, Commented Jul 15, 2020 at 12:25

Yevhen Kuzmovych · Accepted Answer · 2020-07-15 12:32:41Z

3

This method either needs to be static:

class MyModule():
    def __init__(self):
        pass # Constructor
    def dosth(self):
        print("My module is doing something!")

    class more:
        @staticmethod
        def domore():
            print("My module is doing even more!")

with

m = MyModule()
m.more.domore()
# or directly
MyModule.more.domore()

or you need to create an instance of more first:

m = MyModule.more()
m.domore()

edited Jul 15, 2020 at 12:32

answered Jul 15, 2020 at 12:16

Yevhen Kuzmovych

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2 Comments

Tristan Nemoz Over a year ago

I think adding an attribute which is an instance of the more class should also solve the problem, and allows to use m.more the way the OP intends to (from my understanding).

chepner Over a year ago

There isn't really enough information about why the OP wants this design to say whether an instance of more should be added as an attribute.

Drethax · Accepted Answer · 2020-07-15 12:27:52Z

2

Adding () after more solved the problem for me

m.more().domore()

answered Jul 15, 2020 at 12:27

Drethax

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