运算符重载意味着赋予超出其预定义的操作含义的扩展含义。例如运算符 + 用于添加两个整数以及连接两个字符串和合并两个列表。这是可以实现的，因为 ‘+’ 运算符被 int 类和 str 类重载。您可能已经注意到，相同的内置运算符或函数对不同类的对象显示不同的行为，这称为运算符重载。
# Python program to show use of
# + operator for different purposes.
print(1 + 2)
# concatenate two strings
print("Geeks"+"For")
# Product two numbers
print(3 * 4)
# Repeat the String
print("Geeks"*4)
3
GeeksFor
12
GeeksGeeksGeeksGeeks
如何重载Python中的运算符？
考虑到我们有两个对象，它们是一个类的物理表示（用户定义的数据类型），我们必须使用二进制“+”运算符添加两个对象，它会引发错误，因为编译器不知道如何添加两个对象. 因此，我们为运算符定义了一个方法，该过程称为运算符重载。我们可以重载所有现有的运算符，但不能创建新的运算符。为了执行运算符重载，Python 提供了一些特殊函数或魔术函数，当它与特定运算符关联时会自动调用这些函数。例如，当我们使用 + 运算符时，会自动调用魔术方法 add，其中定义了 + 运算符的操作。
重载二进制 + 运算符
当我们在用户定义的数据类型上使用运算符时，会自动调用与该运算符关联的特殊函数或魔术函数。改变操作符的行为就像改变方法或函数的行为一样简单。您在类中定义方法，操作符根据方法中定义的行为工作。当我们使用 + 运算符时，会自动调用魔术方法 add ，其中定义了 + 运算符的操作。通过改变这个魔法方法的代码，我们可以给 + 操作符赋予额外的意义。
代码1
# Python Program illustrate how
# to overload an binary + operator
class A:
def __init__(self, a):
self.a = a
# adding two objects
def __add__(self, o):
return self.a + o.a
ob1 = A(1)
ob2 = A(2)
ob3 = A("Geeks")
ob4 = A("For")
print(ob1 + ob2)
print(ob3 + ob4)
3
GeeksFor
代码2
# Python Program to perform addition
# of two complex numbers using binary
# + operator overloading.
class complex:
def __init__(self, a, b):
self.a = a
self.b = b
# adding two objects
def __add__(self, other):
return self.a + other.a, self.b + other.b
Ob1 = complex(1, 2)
Ob2 = complex(2, 3)
Ob3 = Ob1 + Ob2
print(Ob3)
(3, 5)
重载比较运算符
# Python program to overload
# a comparison operators
class A:
def __init__(self, a):
self.a = a
def __gt__(self, other):
if(self.a>other.a):
return True
else:
return False
ob1 = A(2)
ob2 = A(3)
if(ob1>ob2):
print("ob1 is greater than ob2")
else:
print("ob2 is greater than ob1")
ob2 is greater than ob1
重载相等和小于运算符
# Python program to overload equality
# and less than operators
class A:
def __init__(self, a):
self.a = a
def __lt__(self, other):
if(self.a<other.a):
return "ob1 is lessthan ob2"
else:
return "ob2 is less than ob1"
def __eq__(self, other):
if(self.a == other.a):
return "Both are equal"
else:
return "Not equal"
ob1 = A(2)
ob2 = A(3)
print(ob1 < ob2)
ob3 = A(4)
ob4 = A(4)
print(ob1 == ob2)
ob1 is lessthan ob2
Not equal
用于运算符重载的魔术方法或特殊函数
二元运算符
操作员 魔术方法
+ __add__(self, other)
– __sub__(self, other)
* __mul__(self, other)
/ __truediv__(self, other)
// __floordiv__(self, other)
% __mod__(self, other)
** __pow__(self, other)
>> __rshift__(self, other)
<< __lshift__(self, other)
& __and__(self, other)
| __or__(self, other)
^ __xor__(self, other)
比较运算符
Operator Magic Method
< __lt__(self, other)
> __gt__(self, other)
<= __le__(self, other)
>= __ge__(self, other)
== __eq__(self, other)
!= __ne__(self, other)
赋值运算符
Operator Magic Method
-= __isub__(self, other)
+= __iadd__(self, other)
*= __imul__(self, other)
/= __idiv__(self, other)
//= __ifloordiv__(self, other)
%= __imod__(self, other)
**= __ipow__(self, other)
>>= __irshift__(self, other)
<<= __ilshift__(self, other)
&= __iand__(self, other)
|= __ior__(self, other)
^= __ixor__(self, other)
一元运算符
Operator Magic Method
– __neg__(self)
+ __pos__(self)
~ __invert__(self)
注意：不能更改运算符的操作数数量。例如。您不能将一元运算符重载为二元运算符。以下代码将引发语法错误。
# Python program which attempts to
# overload ~ operator as binary operator
class A:
def __init__(self, a):
self.a = a
# Overloading ~ operator, but with two operands
def __invert__(self, other):
return "This is the ~ operator, overloaded as binary operator."
ob1 = A(2)
ob2 = A(3)
print(ob1~ob2)
https://www.geeksforgeeks.org/operator-overloading-in-python/