Why does python use two underscores for certain things?

Question

I\'m fairly new to actual programming languages, and Python is my first one. I know my way around Linux a bit, enough to get a summer job with it (I\'m still in high school)

Answer 1

A number of other questions are now marked as duplicates of this question, and at least two of them ask what either the __spam__ methods are called, or what the convention is called, and none of the existing answers cover that, so:

There actually is no official name for either.

Many developers unofficially call them "dunder methods", for "Double UNDERscore".

Some people use the term "magic methods", but that's somewhat ambiguous between meaning dunder methods, special methods (see below), or something somewhere between the two.

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There is an official term "special attributes", which overlaps closely but not completely with dunder methods. The Data Model chapter in the reference never quite explains what a special attribute is, but the basic idea is that it's at least one of the following:

• An attribute that's provided by the interpreter itself or its builtin code, like __name__ on a function.
• An attribute that's part of a protocol implemented by the interpreter itself, like __add__ for the + operator, or __getitem__ for indexing and slicing.
• An attribute that the interpreter is allowed to look up specially, by ignoring the instance and going right to the class, like __add__ again.

Most special attributes are methods, but not all (e.g., __name__ isn't). And most use the "dunder" convention, but not all (e.g., the next method on iterators in Python 2.x).

And meanwhile, most dunder methods are special attributes, but not all—in particular, it's not that uncommon for stdlib or external libraries to want to define their own protocols that work the same way, like the pickle protocol.