Calling a class method from within another class method causes AttributeError

[phucly01]

Bug report

Bug description:

class A:
    def __init__(self, cash):
        self.msg = "I am A"
        self.cash = cash
    def __iama(self):
        print(f"{self.msg} and have ${self.cash}")


class B:
    def __init__(self):
        self.A = A(5)
    
    def show(self):
        self.A.__iama()

if __name__ == '__main__':
    B().show()

Error:

Traceback (most recent call last):
  File "/home/fmadmin/workspace/test_automation/src/./example.py", line 19, in <module>
    B().show()
  File "/home/fmadmin/workspace/test_automation/src/./example.py", line 16, in show
    self.A.__iama()
    ^^^^^^^^^^^^^
AttributeError: 'A' object has no attribute '_B__iama'. Did you mean: '_A__iama'?

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[StanFromIreland]

Please see the docs on private name mangling here and the error suggestion.

__*
Class-private names. Names in this category, when used within the context of a class definition, are re-written to use a mangled form to help avoid name clashes between “private” attributes of base and derived classes. See

[phucly01]

Please see the docs on private name mangling here and the error suggestion.

__*
Class-private names. Names in this category, when used within the context of a class definition, are re-written to use a mangled form to help avoid name clashes between “private” attributes of base and derived classes. See

@StanFromIreland Ok thank you. I thought _ and __ are just convention. I didn't know Python actually fails.