What's the Difference Between Single and Double Underscores in Python Object Names?

Demystifying Underscores in Python Object Names

In Python, naming conventions play a crucial role in object naming. Single and double underscores before an object's name hold specific meanings that guide programmers in understanding the scope and accessibility of that object.

Single Underscore (_name)

A single leading underscore in an object's name suggests that it's meant for internal use within the class. It's a way to indicate that the object is not intended to be accessed or modified from outside the class. However, it's important to note that this convention is a guideline rather than an enforced restriction.

Single underscores are also used to denote modules or functions that should not be imported from elsewhere. By prefixing the object's name with an underscore, it signifies to other programmers that it should be treated as a private element.

Double Underscore (__name__)

Double leading underscores are used for name mangling, a technique that modifies the object's name behind the scenes. This transformation replaces the object's name with a modified version that includes the class name and underscores.

According to Python's documentation, double underscores indicate that an object should be treated as a private variable or method within the current class. However, it's essential to understand that name mangling is not absolute. Determined individuals can still access or modify variables marked as private.

Example

Let's consider the following Python class:

class MyClass():
    def __init__(self):
        self.__superprivate = "Hello"
        self._semiprivate = ", world!"

mc = MyClass()
print(mc._semiprivate)  # Accessible
print(mc.__superprivate)  # Not accessible outside the class

In this example, the __superprivate variable is marked as private using double underscores, while the _semiprivate variable uses a single underscore. The __superprivate variable is inaccessible outside the class, while the _semiprivate variable can be accessed but should be considered internal to the class.

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