Dunder functions in Python

https://docs.python.org/3/reference/datamodel.html

• __init__: constructor

• __del__: destructor ?? (use with care)

• __delete__:

• __new__: this is called before __init__

• __get__: read attribute value

• __set__: write attribute value

• __getattr__:

• __getattribute__:

• __setattr__:

• __delattr__:

• __getitem__: used when reading from x[i]

• __setitem__: used when writing to x[i]

• __delitem__: used when deleting

• __missing__:

• __repr__: representation of object as a string

• __str__: human readable representation of object as string

• __lt__, - __gt__, - __le__, - __ge__, - __eq__, - __ne__: comparison

• __format__: used by format() function (and f-strings)

• __hash__: used by hash()

• __bytes__: used by bytes()

• __bool__: used by bool()

• __iter__: used by iter()

• iterator.__next__():

• __reversed__:

• __contains__:

• __dir__: used by dir()

• __call__:

• __len__:

• __length_hint__:

• __enter__: enter context manager

• __exit__: leave context manager

• __objclass__:

• __slots__:

• __init_subclass__:

• __set_name__:

• __prepare__:

• __mro_entries__:

• __classcell__: CPython specific

• __class__:

• __instancecheck__:

• __subclasscheck__:

• __class_getitem__:

• __match_args__:

• __complex__:

• __int__:

• __float__:

• __index__:

• __round__:

• __trunc__:

• __floor__:

• __ceil__:

• __buffer__:

• __release_buffer__:

• __await__:

• __aiter__:

• __anext__:

Arithmetic and related

Functions with the r prefix are the same except that the order of arguments is reversed.

Note: Ternary pow() will not try calling rpow().

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(divmod isn't there in this list.)

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__slot__

• Classes with slots does not have __dict__ (but their instances might??).
  • Saves space.
  • Faster attribute access
• Remark: dataclass has a slots option

See:

• https://stackoverflow.com/questions/472000/usage-of-slots
• https://wiki.python.org/moin/UsingSlots