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Python FTW: Under the Hood

Let's Mangle

Explore Python's name mangling mechanism to understand how the interpreter modifies class member names with double underscores to prevent naming collisions across namespaces. Learn why some mangled names behave unexpectedly and how this impacts variable access and scope management in Python classes.

We'll cover the following...

Typically, we would discourage it, but for now, let’s mangle.

1.

Why does the following code throw an error?
Python 3.5
class Yo(object):
    def __init__(self):
        self.__honey = True
        self.bro = True
print(Yo().bro)
print(Yo()._Yo__honey)
print(Yo().__honey) # Throws error

2.

Let’s try something symmetrical this time:

Python 3.5
class Yo(object):
    def __init__(self):
        # Let's try something symmetrical this time
        self.__honey__ = True
        self.bro = True
print(Yo().bro)
print(Yo()._Yo__honey__) # Throws an error

Why didn’t Yo()._Yo__honey__ work in the code above?

3.

Let's try something new:
Python 3.5
_A__variable = "Some value"
class A(object):
    def some_func(self):
        return __variable # not initialized anywhere yet
print(A().some_func())
print(A().__variable) # Throws an error
...

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