基础知识
实际上，“运算符重载”只是意味着在类方法中拦截内置的操作……当类的实例出现在内置操作中，Python自动调用你的方法，并且你的方法的返回值变成了相应操作的结果。以下是对重载的关键概念的复习：
运算符重载让类拦截常规的Python运算。
类可重载所有Python表达式运算符
类可以重载打印、函数调用、属性点号运算等内置运算
重载使类实例的行为像内置类型。
重载是通过特殊名称的类方法来实现的。
换句话说，当类中提供了某个特殊名称的方法，在该类的实例出现在它们相关的表达式时，Python自动调用它们。正如我们已经学习过的，运算符重载方法并非必须的，并且通常也不是默认的；如果你没有编写或继承一个运算符重载方法，只是意味着你的类不会支持相应的操作。然而，当使用的时候，这些方法允许类模拟内置对象的接口，因此表现得更一致。
以下代码以Python3.6.1为例
操作符重载方法: 类(class)通过使用特殊名称的方法(len(self))来实现被特殊语法(len())的调用
#coding=utf-8
# specialfuns.py 操作符重载方法
# 类(class)通过使用特殊名称的方法(__len__(self))来实现被特殊语法(len())的调用
# 构造 与 析构 方法
class demo1:
# 构造方法, 对象实例化时调用
def __init__(self):
print("构造方法")
# 析构方法, 对象被回收时调用
def __del__(self):
print("析构方法")
# new
class demo2(object):
# __init__之前调用, 一般用于重写父类的__new__方法, 具体使用见 类 文章的 元类 代码部分(http://blog.csdn.net/rozol/article/details/69317339)
def __new__(cls):
print("new")
return object.__new__(cls)
# 算术运算
class demo3:
def __init__(self, num):
self.data = num
# +
def __add__(self, other):
return self.data + other.data
# -
def __sub__(self, other):
return self.data - other.data
# *
def __mul__(self, other):
return self.data * other.data
# /
def __truediv__(self, other):
return self.data / other.data
# //
def __floordiv__(self, other):
return self.data // other.data
# %
def __mod__(self, other):
return self.data % other.data
# divmod()
def __divmod__(self, other):
# 商(10/5),余数(10%5)
return self.data / other.data, self.data % other.data
# **
def __pow__(self, other):
return self.data ** other.data
# <<
def __lshift__(self, other):
return self.data << other.data
# >>
def __rshift__(self, other):
return self.data >> other.data
# &
def __and__(self, other):
return self.data & other.data
# ^
def __xor__(self, other):
return self.data ^ other.data
# |
def __or__(self, other):
return self.data | other.data
class none:
def __init__(self, num):
self.data = num
# 反算术运算符(a+b, 若a不支持算术运算符,则寻找b的算术运算符)(注:位置变换, 在原始函数名前+r)
class demo4:
def __init__(self, num):
self.data = num
# +
def __radd__(self, other):
return other.data + self.data
# -
def __rsub__(self, other):
return other.data - self.data
# *
def __rmul__(self, other):
return other.data * self.data
# /
def __rtruediv__(self, other):
return other.data / self.data
# //
def __rfloordiv__(self, other):
return other.data // self.data
# %
def __rmod__(self, other):
return other.data % self.data
# divmod()
def __rdivmod__(self, other):
return other.data / self.data, other.data % self.data
# **
def __rpow__(self, other):
return other.data ** self.data
# <<
def __rlshift__(self, other):
return other.data << self.data
# >>
def __rrshift__(self, other):
return other.data >> self.data
# &
def __rand__(self, other):
return other.data & self.data
# ^
def __rxor__(self, other):
return other.data ^ self.data
# |
def __ror__(self, other):
return other.data | self.data
# 增量赋值运算,(注:位置同原始函数,在原始函数名前+i)
class demo5():
def __init__(self, num):
self.data = num
# +=
def __iadd__(self, other):
return self.data + other
# -=
def __isub__(self, other):
return self.data - other
# *=
def __imul__(self, other):
return self.data * other
# /=
def __itruediv__(self, other):
return self.data / other
# //=
def __ifloordiv__(self, other):
return self.data // other
# %=
def __imod__(self, other):
return self.data % other
# **=
def __ipow__(self, other):
return self.data ** other
# <<=
def __ilshift__(self, other):
return self.data << other
# >>=
def __irshift__(self, other):
return self.data >> other
# &=
def __iand__(self, other):
return self.data & other
# ^=
def __ixor__(self, other):
return self.data ^ other
# |=
def __ior__(self, other):
return self.data | other
# 比较运算符
class demo6:
def __init__(self, num):
self.data = num
# <
def __lt__(self, other):
return self.data < other.data
# <=
def __le__(self, other):
return self.data <= other.data
# ==
def __eq__(self, other):
return self.data == other.data
# !=
def __ne__(self, other):
return self.data != other.data
# >
def __gt__(self, other):
return self.data > other.data
# >=
def __ge__(self, other):
return self.data >= other.data
# 一元操作符
class demo7:
def __init__(self, num):
self.data = num
# + 正号
def __pos__(self):
return +abs(self.data)
# - 负号
def __neg__(self):
return -abs(self.data)
# abs() 绝对值
def __abs__(self):
return abs(self.data)
# ~ 按位取反
def __invert__(self):
return ~self.data
# complex() 字符转数字
def __complex__(self):
return 1+2j
# int() 转为整数
def __int__(self):
return 123
# float() 转为浮点数
def __float__(self):
return 1.23
# round() 近似值
def __round__(self):
return 1.123
# 格式化
class demo8:
# print() 打印
def __str__(self):
return "This is the demo."
# repr() 对象字符串表示
def __repr__(self):
return "This is a demo."
# bytes() 对象字节字符串表现形式
def __bytes__(self):
return b"This is one demo."
# format() 格式化
def __format__(self, format_spec):
return self.__str__()
# 属性访问
class demo9:
# 获取(不存在)属性
def __getattr__(self):
print ("访问的属性不存在")
# getattr() hasattr() 获取属性
def __getattribute__(self, attr):
print ("访问的属性是%s"%attr)
return attr
# setattr() 设置属性
def __setattr__(self, attr, value):
print ("设置 %s 属性值为 %s"%(attr, value))
# delattr() 删除属性
def __delattr__(self, attr):
print ("删除 %s 属性"%attr)
# ===================================================================
# 描述器(类(test1)的实例出现在属主类(runtest)中,这些方法才会调用)(注:函数调用,这些方法不会被调用)
class test1:
def __init__(self, value = 1):
self.value = value * 2
def __set__(self, instance, value):
print("set %s %s %s"%(self, instance, value))
self.value = value * 2
def __get__(self, instance, owner):
print("get %s %s %s"%(self, instance, owner))
return self.value
def __delete__(self, instance):
print("delete %s %s"%(self, instance))
del self.value
class test2:
def __init__(self, value = 1):
self.value = value + 0.3
def __set__(self, instance, value):
print("set %s %s %s"%(self, instance, value))
instance.t1 = value + 0.3
def __get__(self, instance, owner):
print("get %s %s %s"%(self, instance, owner))
return instance.t1
def __delete__(self, instance):
print("delete %s %s"%(self, instance))
del self.value
class runtest:
t1 = test1()
t2 = test2()
# ---
# 自定义property
class property_my:
def __init__(self, fget=None, fset=None, fdel=None):
self.fget = fget
self.fset = fset
self.fdel = fdel
# 对象被获取(self自身, instance调用该对象的对象(demo9), owner调用该对象的对象类对象(demo9))
def __get__(self, instance, owner):
print("get %s %s %s"%(self, instance, owner))
return self.fget(instance)
# 对象被设置属性时
def __set__(self, instance, value):
print("set %s %s %s"%(self, instance, value))
self.fset(instance, value)
# 对象被删除时
def __delete__(self, instance):
print("delete %s %s"%(self, instance))
self.fdel(instance)
class demo10:
def __init__(self):
self.num = None
def setvalue(self, value):
self.num = value
def getvalue(self):
return self.num
def delete(self):
del self.num
x = property_my(getvalue, setvalue, delete)
# ===================================================================
# 自定义容器
class lis:
def __init__(self, *args):
self.lists = args
self.size = len(args)
self.startindex = 0
self.endindex = self.size
# len() 容器元素数量
def __len__(self):
return self.size;
# lis[1] 获取元素
def __getitem__(self, key = 0):
return self.lists[key]
# lis[1] = value 设置元素
def __setitem__(self, key, value):
pass
# del lis[1] 删除元素
def __delitem__(self, key):
pass
# 返回迭代器
def __iter__(self):
return self
# rversed() 反向迭代器
def __reversed__(self):
while self.endindex > 0:
self.endindex -= 1
yield self[self.endindex]
# next() 迭代器下个元素
def __next__(self):
if self.startindex >= self.size:
raise StopIteration # 控制迭代器结束
elem = self.lists[self.startindex]
self.startindex += 1
return elem
# in / not in
def __contains__(self, item):
for i in self.lists:
if i == item:
return True
return False
# yield 生成器(执行一次返回,下次继续执行后续代码返回)
def yielddemo():
num = 0
while 1: # 1 == True; 0 == False
if num >= 10:
raise StopIteration
num += 1
yield num
# 能接收数据的生成器
def yielddemo_1():
while 1:
num = yield
print(num)
# with 自动上下文管理
class withdemo:
def __init__(self, value):
self.value = value
# 返回值为 as 之后的值
def __enter__(self):
return self.value
# 执行完成,退出时的数据清理动作
def __exit__(self, exc_type, exc_value, traceback):
del self.value
if __name__ == "__main__":
# 构造与析构
d1 = demo1()
del d1
# new
d2 = demo2()
# 算术运算符
d3 = demo3(3)
d3_1 = demo3(5)
print(d3 + d3_1)
print(d3 - d3_1)
print(d3 * d3_1)
print(d3 / d3_1)
print(d3 // d3_1)
print(d3 % d3_1)
print(divmod(d3, d3_1))
print(d3 ** d3_1)
print(d3 << d3_1)
print(d3 >> d3_1)
print(d3 & d3_1)
print(d3 ^ d3_1)
print(d3 | d3_1)
# 反运算符
d4 = none(3)
d4_1 = demo4(5)
print(d4 + d4_1)
print(d4 - d4_1)
print(d4 * d4_1)
print(d4 / d4_1)
print(d4 // d4_1)
print(d4 % d4_1)
print(divmod(d4, d4_1))
print(d4 ** d4_1)
print(d4 << d4_1)
print(d4 >> d4_1)
print(d4 & d4_1)
print(d4 ^ d4_1)
print(d4 | d4_1)
# 增量赋值运算(测试时注释其他代码)
d5 = demo5(3)
d5 <<= 5
d5 >>= 5
d5 &= 5
d5 ^= 5
d5 |= 5
d5 += 5
d5 -= 5
d5 *= 5
d5 /= 5
d5 //= 5
d5 %= 5
d5 **= 5
print(d5)
# 比较运算符
d6 = demo6(3)
d6_1 = demo6(5)
print(d6 < d6_1)
print(d6 <= d6_1)
print(d6 == d6_1)
print(d6 != d6_1)
print(d6 > d6_1)
print(d6 >= d6_1)
# 一元操作符(测试时注释其他代码)
d7 = demo7(-5)
num = +d7
num = -d7
num = abs(d7)
num = ~d7
print(num)
print(complex(d7))
print(int(d7))
print(float(d7))
print(round(d7))
# 格式化
d8 = demo8()
print(d8)
print(repr(d8))
print(bytes(d8))
print(format(d8, ""))
# 属性访问
d9 = demo9()
setattr(d9, "a", 1) # => 设置 a 属性值为 1
print(getattr(d9, "a")) # => a / 访问的属性是a
print(hasattr(d9, "a")) # => True / 访问的属性是a
delattr(d9, "a") # 删除 a 属性
# ---
d9.x = 100 # => 设置 x 属性值为 100
print(d9.x) # => x / 访问的属性是x
del d9.x # => 删除 x 属性
# 描述器
r = runtest()
r.t1 = 100 # => <__main__.test1> <__main__.runtest> 100
print(r.t1) # => 200 / <__main__.test1> <__main__.runtest> <class '__main__.runtest'>
del r.t1 # => <__main__.test1> <__main__.runtest>
r.t2 = 200 # => <__main__.test2> <__main__.runtest> 200 / <__main__.test1> <__main__.runtest> 200.3
print(r.t2) # => 400.6 / <__main__.test2> <__main__.runtest> <class '__main__.runtest'> / <__main__.test1> <__main__.runtest> <class '__main__.runtest'>
del r.t2 # <__main__.test2> <__main__.runtest>
# ---
# 自定义property
d10 = demo10()
d10.x = 100; # => <__main__.property_my> <__main__.demo10> 100
print(d10.x) # => 100 / <__main__.property_my> <__main__.demo10> <class '__main__.demo10'>
del d10.x # => <__main__.property_my> <__main__.demo10>
d10.num = 200;
print(d10.num) # => 200
del d10.num
# 自定义容器(迭代器Iterator)
lis = lis(1,2,3,4,5,6)
print(len(lis))
print(lis[1])
print(next(lis))
print(next(lis))
print(next(lis))
for i in lis:
print (i)
for i in reversed(lis):
print (i)
print(3 in lis)
print(7 in lis)
print(3 not in lis)
print(7 not in lis)
# yield 生成器(可迭代对象Iterable)
for i in yielddemo():
print (i)
# ---
iters = iter(yielddemo())
print(next(iters))
print(next(iters))
# --- 发送数据给生成器 ---
iters = yielddemo_1()
next(iters)
iters.send(6) # 发送数据并执行
iters.send(10)
# with 自动上下文管理
with withdemo("Less is more!") as s:
print(s)
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持毛票票。