Python Magic Methods

There are far more magic methods in Python than we could ever hope to cover. However, we believe that the arithmetic and boolean magic methods are fairly intuitive to use, and so don't deserve special attention.

What are magic methods? They're everything in object-oriented Python. They're special methods that you can define to add "magic" to your classes. They're always surrounded by double underscores (e.g. __init__ or __lt__).

Magic Method	When it gets invoked (example)	Explanation
`__new__(cls [,...])`	`instance = MyClass(arg1, arg2)`	`__new__` is called on instance creation
`__init__(self [,...])`	`instance = MyClass(arg1, arg2)`	`__init__` is called on instance creation
`__cmp__(self, other)`	`self == other`, `self > other`, etc.	Called for any comparison
`__pos__(self)`	`+self`	Unary plus sign
`__neg__(self)`	`-self`	Unary minus sign
`__invert__(self)`	`~self`	Bitwise inversion
`__index__(self)`	`x[self]`	Conversion when object is used as index
`__nonzero__(self)`	`bool(self)`	Boolean value of the object
`__getattr__(self, name)`	`self.name # name doesn't exist`	Accessing nonexistent attribute
`__setattr__(self, name, val)`	`self.name = val`	Assigning to an attribute
`__delattr__(self, name)`	`del self.name`	Deleting an attribute
`__getattribute__(self, name)`	`self.name`	Accessing any attribute
`__getitem__(self, key)`	`self[key]`	Accessing an item using an index
`__setitem__(self, key, val)`	`self[key] = val`	Assigning to an item using an index
`__delitem__(self, key)`	`del self[key]`	Deleting an item using an index
`__iter__(self)`	`for x in self`	Iteration
`__contains__(self, value)`	`value in self`, `value not in self`	Membership tests using `in`
`__call__(self [,...])`	`self(args)`	"Calling" an instance
`__enter__(self)`	`with self as x:`	`with` statement context managers
`__exit__(self, exc, val, trace)`	`with self as x:`	`with` statement context managers
`__getstate__(self)`	`pickle.dump(pkl_file, self)`	Pickling
`__setstate__(self)`	`data = pickle.load(pkl_file)`	Pickling