Why do some functions have underscores “__” before and after the function name?

Question

This seems to occur a lot, and was wondering if this was a requirement in the Python language, or merely a matter of convention?

Also, could someone name and explain which functions tend to have underscores, and why (__init__, for instance)?

Answer 1

The reason behind some functions have underscores “__” before and after the function name because it is the Naming Style in Python:-

Below are the details of some of the important naming styles in Python:-

• The use of _single_leading_underscore is for weak "internal use" indicator.

• The single_trailing_underscore_ is used to avoid conflicts with Python keyword, 

• The __double_leading_underscore is used when naming a class attribute, invokes name mangling (inside class AbcPdf, __Abc becomes _AbcPdf__Abc).

• While the __double_leading_and_trailing_underscore__ is called as "magic" objects or attributes that live in user-controlled namespaces.