How can access to internal methods and variables of a class be restricted in Python?

Python does not have a strict access restriction system like some other languages (for example, private in Java or C++). However, there are conventions and mechanisms that help indicate internal methods and variables:

• A single underscore _var indicates that the variable or method is intended for internal use (protected by convention).
• A double underscore __var activates name mangling, where the variable name is changed to _ClassName__var, making external access more difficult.

Example:

class MyClass:
    def __init__(self):
        self.public_var = 1
        self._protected_var = 2
        self.__private_var = 3

    def __private_method(self):
        print("This is a private method")

obj = MyClass()
print(obj.public_var)        # 1
print(obj._protected_var)    # 2 (possible, but not recommended)
# print(obj.__private_var)   # AttributeError
print(obj._MyClass__private_var)  # 3 (access via name mangling)

# Calling a private method
# obj.__private_method()     # Error
obj._MyClass__private_method()  # Works

Thus, double underscores serve as a way to limit access, but it is more of a convention and a bypass mechanism rather than strict protection.