All special methods in python
This part of the content can refer to the official website https://docs.python.org/3/reference/datamodel.html#special-method-names
There are a total of 83 special methods in python, of which 47 are used for arithmetic operations, bit operations and comparison operations. According to the arrangement in "Smooth Python", I excerpted the following two tables
Table 1: Special methods not related to operators
| category | method name |
| String/byte sequence representation | __repr__、__str__、__format__、__bytes__ |
| Numeric conversion | __abs__、__bool__、__complex__、__int__、__float__、__hash__、__index__ |
| Collection simulation | __len__、__getitem__、__setitem__、__delitem__、__contains__ |
| iterate enumeration | __iter__、__reversed__、__next__ |
| callable mock | __call__ |
| context management | __enter__、__exit__ |
| instance creation and destruction | __new__、__init__、__del__ |
| property management | __getattr__、__getattribute__、__setattr__、__delattr__、__dir__ |
| property descriptor | __get__、__set__、__delete__ |
| Class related services | __prepare__、__instancecheck__、__subclasscheck__ |
Table 2: Special methods associated with operators
| category | Method name and corresponding operator |
| unary operator | __neg__ -、__pos__ +、__abs__ abs() |
| Numerous comparison operators | __lt__ <、__le__ <=、__eq__ ==、__ne__ !=、__gt__ >、__ge__>= |
| arithmetic operators | __add__ +、__sub__ -、__mul__ *、__truediv__ /、__floordiv__ //、 __mod__ %、__divmod__ divmod()、__pow__ **或pow()、__round__ round() |
| reverse arithmetic operator | __radd __ 、 __ rsub __ 、 __ rmul __ 、 __ rtruediv __ 、 __ rfloordiv __ 、 __ rmod __ 、 __ rdivmod __ 、 __ rpow__ |
| Increment assignment arithmetic operator | __iadd __ 、 __ isub __ 、 __ imul __ 、 __ itruediv __ 、 __ ifloordiv __ 、 __ imod __ 、 __ ipow__ |
| bitwise operators | __invert__ ~、__lshift__ <<、__rshift__ >>、__and__ &、__or__ |、__xor__ ^ |
| reverse bitwise operator | __rlshift__、__rrshift__、__rand__、__rxor__、__ror__ |
| Increment assignment bitwise operator | __ilshift__、__irshift__、__iand__、__ixor__、__ior__ |
How to use special methods:
1. The invocation of special methods is implicit, and usually your code does not need to use special methods directly. Unless there is a lot of metaprogramming, the frequency of calling special methods directly should be far less than the number of times you are going to implement them. The only exception might be the __init__ method, which may be used frequently in your code to call the superclass's constructor in your subclass's __init__ method.
2. Using special methods through built-in functions (such as len, iter, str, etc.) is the best choice. Not only do these built-in functions call special methods, they often provide additional benefits, but they are faster for built-in classes.
3. Don't arbitrarily add special methods, such as __foo__, etc., because although this name is not used internally by python now, it will not be necessary in the future.
- "Fluid Python"
## Original link: http://www.cnblogs.com/liao-sir/p/8416081.html