Where is the Python documentation for the special methods? (__init__, __new__, __len__, …)

Question

Where is a complete list of the special double-underscore/dunder methods that can be used in classes? (e.g., __init__, __new__, __len__, __add__)

Answer 1

Please take a look at the special method names section in the Python language reference.

Answer 2

Dive Into Python has an excellent appendix for them.

Answer 3

If, like me, you want a plain, unadorned list, here it is. I compiled it based on the Python documentation link from the accepted answer.

__abs__
__add__
__and__
__call__
__class__
__cmp__
__coerce__
__complex__
__contains__
__del__
__delattr__
__delete__
__delitem__
__delslice__
__dict__
__div__
__divmod__
__eq__
__float__
__floordiv__
__ge__
__get__
__getattr__
__getattribute__
__getitem__
__getslice__
__gt__
__hash__
__hex__
__iadd__
__iand__
__idiv__
__ifloordiv__
__ilshift__
__imod__
__imul__
__index__
__init__
__instancecheck__
__int__
__invert__
__ior__
__ipow__
__irshift__
__isub__
__iter__
__itruediv__
__ixor__
__le__
__len__
__long__
__lshift__
__lt__
__metaclass__
__mod__
__mro__
__mul__
__ne__
__neg__
__new__
__nonzero__
__oct__
__or__
__pos__
__pow__
__radd__
__rand__
__rcmp__
__rdiv__
__rdivmod__
__repr__
__reversed__
__rfloordiv__
__rlshift__
__rmod__
__rmul__
__ror__
__rpow__
__rrshift__
__rshift__
__rsub__
__rtruediv__
__rxor__
__set__
__setattr__
__setitem__
__setslice__
__slots__
__str__
__sub__
__subclasscheck__
__truediv__
__unicode__
__weakref__
__xor__

Answer 4

Here is a complete reference of all the Python magic methods.

Answer 5

See Python Quick reference

Answer 6

Do this if you prefer reading documentation from a CLI instead of the browser.

$ pydoc SPECIALMETHODS

Answer 7

For somebody who is relatively new to Python, and for whom the documentation is often not quite accessible enough (like myself): somebody wrote a nice introduction with lots of examples on how the special (magic) methods work, how to use them, etc.

Answer 8

Familiarize yourself with the dir function.

Answer 9

Python's double underscore ("dunder") methods are also known as datamodel methods because they are at the core of Python's data model, providing a protocol for customizing (overloading) built-in methods. This is the reason why they are listed in the "Data Model" section of the Python's documentation.