Where is the Python documentation for the special methods? (__init__, __new__, __len__, ...)
PythonClassMagic MethodsPython Problem Overview
Where is a complete list of the special double-underscore/dunder methods that can be used in classes? (e.g., __init__, __new__, __len__, __add__)
Python Solutions
Solution 1 - Python
Please take a look at the special method names section in the Python language reference.
Solution 2 - Python
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__
Solution 3 - Python
Dive Into Python has an excellent appendix for them.
Solution 4 - Python
Solution 5 - Python
Do this if you prefer reading documentation from a CLI instead of the browser.
$ pydoc SPECIALMETHODS
Solution 6 - Python
Solution 7 - Python
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.
Solution 8 - Python
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.
Solution 9 - Python
Following on from @Justin's answer, he included 95 items, here are the dunder methods I could infer: # 105 on 2.7 and 108 on 3.10:
from functools import partial
from itertools import chain
# From https://github.com/Suor/funcy/blob/0ee7ae8/funcy/funcs.py#L34-L36
def rpartial(func, *args):
"""Partially applies last arguments."""
return lambda *a: func(*(a + args))
dunders = tuple(filter(rpartial(str.startswith, "__"),
frozenset(chain.from_iterable((
# https://docs.python.org/3/library/stdtypes.html
chain.from_iterable(map(dir, (int, float, complex,
list, tuple, range,
str, bytes,
# 2.7: unicode,
bytearray, memoryview,
set, frozenset, dict,
type, None, Ellipsis,
NotImplemented, object)
)),
# https://docs.python.org/3/library/functions.html#dir
dir(),
# https://docs.python.org/3/library/stdtypes.html#special-attributes
("__dict__", "__class__", "__bases__", "__name__",
"__qualname__", "__mro__", "__subclasses__",
# https://docs.python.org/3/reference/datamodel.html#slots
"__slots__")
)))))
Output on 3.10:
('__abs__',
'__abstractmethods__',
'__add__',
'__alloc__',
'__and__',
'__annotations__',
'__base__',
'__bases__',
'__basicsize__',
'__bool__',
'__builtins__',
'__cached__',
'__call__',
'__ceil__',
'__class__',
'__class_getitem__',
'__contains__',
'__delattr__',
'__delitem__',
'__dict__',
'__dictoffset__',
'__dir__',
'__divmod__',
'__doc__',
'__enter__',
'__eq__',
'__exit__',
'__file__',
'__flags__',
'__float__',
'__floor__',
'__floordiv__',
'__format__',
'__ge__',
'__getattribute__',
'__getformat__',
'__getitem__',
'__getnewargs__',
'__gt__',
'__hash__',
'__iadd__',
'__iand__',
'__imul__',
'__index__',
'__init__',
'__init_subclass__',
'__instancecheck__',
'__int__',
'__invert__',
'__ior__',
'__isub__',
'__itemsize__',
'__iter__',
'__ixor__',
'__le__',
'__len__',
'__loader__',
'__lshift__',
'__lt__',
'__mod__',
'__module__',
'__mro__',
'__mul__',
'__name__',
'__ne__',
'__neg__',
'__new__',
'__or__',
'__package__',
'__pos__',
'__pow__',
'__prepare__',
'__qualname__',
'__radd__',
'__rand__',
'__rdivmod__',
'__reduce__',
'__reduce_ex__',
'__repr__',
'__reversed__',
'__rfloordiv__',
'__rlshift__',
'__rmod__',
'__rmul__',
'__ror__',
'__round__',
'__rpow__',
'__rrshift__',
'__rshift__',
'__rsub__',
'__rtruediv__',
'__rxor__',
'__set_format__',
'__setattr__',
'__setitem__',
'__sizeof__',
'__slots__',
'__spec__',
'__str__',
'__sub__',
'__subclasscheck__',
'__subclasses__',
'__subclasshook__',
'__text_signature__',
'__truediv__',
'__trunc__',
'__weakrefoffset__',
'__xor__')
Solution 10 - Python
Familiarize yourself with the dir function.