Python Dunder Methods Cheat Sheet – Be on the Right Side of Change

When searching for a list of dunder methods with explanations, i.e., a cheat sheet on Python magic methods, I only found a couple of resources all over the web—each covering only a fraction of dunder methods. So, here’s my collection of 127 dunder methods (also called “magic methods”) from those sources, sorted alphabetically. I provide the data in three forms.

Python Dunder Methods Table with Explanation

Name	Description
`__abs__`	Absolute value of a given argument
`__add__`	Addition x + y for x and y arguments
`__aenter__`	Like `__enter__()` but must return an awaitable
`__aexit__`	Like `__exit__()` but must return an awaitable
`__aiter__`	Returns an asynchronous iterator
`__and__`	Bitwise “AND” of a and b
`__anext__`	Return an awaitable as the next value of the iterator argument
`__annotations__`	A dict containing annotations (values) associated to parameter names (keys)
`__await__`	Return an iterator to implement awaitable objects
`__bool__`	Truth value testing for built-in `bool()` returning `False` or `True`. If undefined, call `__len__()`
`__bytes__`	Called by `bytes()` to compute a byte-string representation of an object. Must return a `bytes` object.
`__call__`	Called when a given instance is called as a function
`__ceil__`	Implement math function `ceil()`
`__complex__`	Implement the built-in functions `complex()` to create a new complex number
`__contains__`	Implements the Python `in` operator to check membership.
`__del__`	Called when the instance is about to be destroyed
`__delattr__`	Delete an attribute
`__delete__`	Delete the attribute on an instance of the owner class.
`__delitem__`	Remove the value of the first argument at index as defined in second argument.
`__dir__`	Called when `dir(x)` is called on object `x`.
`__div__`	The division operator (`/`) in Python 2 is implemented by this dunder method. For Python 3, the `__truediv__()` method is used instead.
`__divmod__`	Implements the `divmod()` built-in method. Python’s built-in `divmod(a, b)` function takes two integer or float numbers a and b as input arguments and returns a tuple `(a // b, a % b)`.
`__enter__`	Enter the runtime context related to this object.
`__eq__`	Rich comparison: `x==y` calls `x.__eq__(y)`
`__exit__`	Exit the runtime context related to this object.
`__float__`	Called to implement the built-in function `float()`.
`__floor__`	Implements behavior for `math.floor()`, i.e., rounding down to the nearest integer.
`__floordiv__`	Implements `a//b`
`__format__`	The Python `__format__()` method implements the built-in `format()` function as well as the `string.format()` method. So, when you call `format(x, spec)` or `string.format(spec)`, Python attempts to call `x.__format__(spec)`. The return value is a string.
`__ge__`	Return whether `x` is greater than or equal `y`
`__get__`	Called on the attribute type to get a class attribute or instance attribute of the owner class.
`__getattr__`	Called when the default attribute access fails with an `AttributeError`
`__getattribute__`	Called unconditionally to implement attribute accesses for instances of the class. If the class also defines `__getattr__()`, this method won’t be called unless `__getattribute__()` either calls it explicitly or raises an `AttributeError`.
`__getitem__`	Return the value of `a` at index `b`.
`__gt__`	Returns the result of the greater than operation `x > y`
`__hash__`	Called by built-in function `hash()`, should return an integer.
`__hex__`	Does not work for Python 3. Use `__index__()` instead.
`__iadd__`	`a = iadd(a, b)` is equivalent to `a += b`.
`__iand__`	`a = iand(a, b)` is equivalent to `a &= b`.
`__idiv__`	`a = idiv(a, b)` is equivalent to `a /= b` in Python 2. In Python 3, this is replaced by `__itruediv__`.
`__ifloordiv__`	`a = ifloordiv(a, b)` is equivalent to `a //= b`.
`__ilshift__`	`a = ilshift(a, b)` is equivalent to `a <<= b`.
`__imatmul__`	`a = imatmul(a, b)` is equivalent to `a @= b`.
`__imod__`	`a = imod(a, b)` is equivalent to `a %= b`.
`__import__`	Import a library by name. For example, to import the NumPy library dynamically, you could run `__import__('numpy')`.
`__imul__`	`a = imul(a, b)` is equivalent to `a *= b`.
`__index__`	Returns the object converted to an integer. This is used for many built-in functions such as `oct()`, `hex()`, or `bin()`.
`__init__`	Called after the instance has been created (by `__new__()`), but before it is returned to the caller.
`__init_subclass__`	This method is called whenever the class defining it is subclassed.
`__instancecheck__`	Return `True` if instance should be considered a direct or indirect `instance` of `class`. If defined, called to implement `isinstance(instance, class)`.
`__int__`	Called to implement the built-in function `int()`.
`__invert__(x)`	Return the bitwise inverse `~x` of the number `x`.
`__ior__`	`a = ior(a, b)` is equivalent to `a \|= b`.
`__ipow__`	`a = ipow(a, b)` is equivalent to `a **= b`.
`__irshift__`	`a = irshift(a, b)` is equivalent to `a >>= b`.
`__isub__`	`a = isub(a, b)` is equivalent to `a -= b`.
`__iter__`	This method is called when an iterator is required for a container. It returns a new iterator object that can iterate over all the objects in the container.
`__itruediv__`	`a = itruediv(a, b)` is equivalent to `a /= b`.
`__ixor__`	`a = ixor(a, b)` is equivalent to `a ^= b`.
`__le__`	Returns `True` if the former is less than or equal to the latter argument, i.e., `x <= y`
`__len__`	Called to implement the built-in function `len()`. Returns the length of the object >= 0. An object that doesn’t define `__bool__()` is considered `False` if its `__len__()` method returns zero.
`__lshift__`	Return x shifted left by y.
`__lt__`	Returns the result of the less than operation `x < y`
`__matmul__`	Return `a @ b`.
`__missing__`	Called by dict.__getitem__() to implement self[key] for dict subclasses when key is not in the dictionary.
`__mod__`	Return x % y.
`__mul__`	Return a * b, for a and b numbers.
`__ne__`	Rich comparison: `x!=y` and `x<>y` call `x.__ne__(y)`
`__neg__`	Return `x` negated (`-x`).
`__new__`	Called to create a new instance of a given class `cls`.
`__next__`	Return the next item from the container.
`__oct__`	Does not work for Python 3. Use `__index__()` instead.
`__or__`	Return the bitwise or of a and b.
`__pow__`	Return a ** b, for a and b numbers.
`__radd__`	Called to implement the binary arithmetic operation + with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rand__`	Called to implement the binary arithmetic operation & (`__and__`) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rdiv__`	Called to implement the binary arithmetic operation / (`__div__`) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rdivmod__`	Called to implement the binary arithmetic operation `divmod()` with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__repr__`	Called by the `repr()` built-in function to compute the “official” string representation of an object.
`__reversed__`	Called (if present) by the `reversed()` built-in to implement reverse iteration. It should return a new iterator object that iterates over all the objects in the container in reverse order.
`__rfloordiv__`	Called to implement the binary arithmetic operation // (__floordiv__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rlshift__`	Called to implement the binary arithmetic operation << (__lshift__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rmatmul__`	Called to implement the matmul operation @ (__matmul__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rmod__`	Called to implement the binary arithmetic operation % (__mod__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rmul__`	Called to implement the binary arithmetic operation * (__mul__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__ror__`	Called to implement the binary arithmetic operation \| (__or__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__round__`	Called to implement the built-in function `round()` and math functions `trunc()`, `floor()` and `ceil()`.
`__rpow__`	Called to implement the arithmetic multiplication operation ** (`__pow__`) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rrshift__`	Called to implement the binary arithmetic operation >> (`__rshift__`) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rshift__`	Return a shifted right by b, i.e., `a >> b`.
`__rsub__`	Called to implement the binary arithmetic operation – (__sub__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rtruediv__`	Called to implement the binary arithmetic operation / (__truediv__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__rxor__`	Called to implement the binary arithmetic operation ^ (__xor__) with reflected (swapped) operands. Only called if the left operand does not support the corresponding operation and the operands are of different types.
`__set__`	Called to set the attribute on an instance of the owner class to a new value.
`__set_name__`	Called at the time the owning class owner is created. The descriptor has been assigned to name.
`__setattr__`	Called when you assign an attribute via `setattr()` instead of the normal mechanism of storing the value in the instance dictionary.
`__setitem__`	Set a given element at a given index to a new value.
`__sizeof__`	Returns the internal size in bytes for the given object
`__str__`	Called by `str(object)` and the built-in functions `format()` and `print()` to compute the “informal” or printable string representation of an object.
`__sub__`	Return `a - b`.
`__subclasscheck__`	Return true if subclass should be considered a (direct or indirect) subclass of class. If defined, called to implement issubclass(subclass, class).
`__subclasses__`	Finds all subclasses of a given class.
`__truediv__`	Return a / b where 2/3 is .66 rather than 0. This is also known as “true” division.
`__trunc__`	Called to implement the `math.trunc()` function.
`__xor__`	Return the bitwise exclusive or of a and b.

Table: List of Dunder Methods with Explanations

To get the list of sources used to create this table, please scroll down to the end of the article.

Python Special Attributes

Python has multiple special attributes that are defined per default for each class such as __name__, __module__, __dict__, __bases__, __doc__, and __annotations__.

Attribute	Type	Description
`__name__`	`str`	The name of the class
`__module__`	`str`	The string name of the module where the class is defined
`__dict__`	`dict`	The dictionary with the namespace of the class
`__bases__`	`tuple`	A tuple with base classes of this class
`__doc__`	`str` or `None`	The documentation of the class as a string. If no documentation is defined, `None`.
`__annotations__`	`dict`	A dictionary with variable annotations in this class

You can find them explained here:

Python Special Attri b utes

Python Dunder Methods — One Method Per Line

__abs__
__add__
__aenter__
__aexit__
__aiter__
__and__
__anext__
__await__
__bool__
__bytes__
__call__
__ceil__
__class__
__class_getitem__
__cmp__
__coerce__
__complex__
__contains__
__del__
__delattr__
__delete__
__delitem__
__delslice__
__dict__
__dir__
__div__
__divmod__
__enter__
__eq__
__exit__
__float__
__floor__
__floordiv__
__format__
__fspath__
__ge__
__get__
__getattr__
__getattribute__
__getitem__
__getnewargs__
__getslice__
__gt__
__hash__
__hex__
__iadd__
__iand__
__idiv__
__ifloordiv__
__ilshift__
__imatmul__
__imod__
__import__
__imul__
__index__
__init__
__init_subclass__
__instancecheck__
__int__
__invert__
__ior__
__ipow__
__irshift__
__isub__
__iter__
__itruediv__
__ixor__
__le__
__len__
__length_hint__
__long__
__lshift__
__lt__
__matmul__
__metaclass__
__missing__
__mod__
__mro__
__mul__
__ne__
__neg__
__new__
__next__
__nonzero__
__oct__
__or__
__pos__
__pow__
__prepare__
__radd__
__rand__
__rcmp__
__rdiv__
__rdivmod__
__reduce__
__reduce_ex__
__repr__
__reversed__
__rfloordiv__
__rlshift__
__rmatmul__
__rmod__
__rmul__
__ror__
__round__
__rpow__
__rrshift__
__rshift__
__rsub__
__rtruediv__
__rxor__
__set__
__set_name__
__setattr__
__setitem__
__setslice__
__sizeof__
__slots__
__str__
__sub__
__subclasscheck__
__subclasses__
__truediv__
__trunc__
__unicode__
__weakref__
__xor__

Python Dunder Methods as a List of Strings

In case you need them as a Python list for copy&paste, here it is:

['__abs__', '__add__', '__aenter__', '__aexit__', '__aiter__', '__and__', '__anext__', '__await__', '__bool__', '__bytes__', '__call__', '__ceil__', '__class__', '__class_getitem__', '__cmp__', '__coerce__', '__complex__', '__contains__', '__del__', '__delattr__', '__delete__', '__delitem__', '__delslice__', '__dict__', '__dir__', '__div__', '__divmod__', '__enter__', '__eq__', '__exit__', '__float__', '__floor__', '__floordiv__', '__format__', '__fspath__', '__ge__', '__get__', '__getattr__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__hex__', '__iadd__', '__iand__', '__idiv__', '__ifloordiv__', '__ilshift__', '__imatmul__', '__imod__', '__import__', '__imul__', '__index__', '__init__', '__init_subclass__', '__instancecheck__', '__int__', '__invert__', '__ior__', '__ipow__', '__irshift__', '__isub__', '__iter__', '__itruediv__', '__ixor__', '__le__', '__len__', '__length_hint__', '__long__', '__lshift__', '__lt__', '__matmul__', '__metaclass__', '__missing__', '__mod__', '__mro__', '__mul__', '__ne__', '__neg__', '__new__', '__next__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__prepare__', '__radd__', '__rand__', '__rcmp__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rfloordiv__', '__rlshift__', '__rmatmul__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__set__', '__set_name__', '__setattr__', '__setitem__', '__setslice__', '__sizeof__', '__slots__', '__str__', '__sub__', '__subclasscheck__', '__subclasses__', '__truediv__', '__trunc__', '__unicode__', '__weakref__', '__xor__']

References and Sources