当与set一起使用时，它执行联合操作。

在Python中，|=(ior)类似于联合运算。 例如，如果x=5和x|=5，那么两个值都将首先转换为二进制值，然后执行并集操作，我们得到答案5。

在Python和许多其他编程语言中，|是位或操作。|=之于|，正如+=之于+，即运算和赋值的组合。

var |= value是var = var | value的缩写。

一个常见的用例是合并两个集合:

>>> a = {1,2}; a |= {3,4}; print(a)
{1, 2, 3, 4}

它表示按位或操作。

例子:

x = 5
x |= 3 #which is similar to x = x | 3
print(x)

答案:7

它是如何工作的?

The binary of 5 is : 0 1 0 1
The binary of 3 is : 0 0 1 1

OR operation : (If one of both sides are 1/True then result is 1/True)

0 1 0 1  #Binary of 5
0 0 1 1  #Binary of 3
---------------------
0 1 1 1  #Binary of 7

所以答案是7

它对赋值的左侧和右侧执行二进制位或运算，然后将结果存储在左侧变量中。

http://docs.python.org/reference/expressions.html#binary-bitwise-operations

希望这也能帮助其他人理解:

dict1 = {'a': 'dict1', 'b': 'dict1', 'c': 'dict1'}
dict2 = {'c': 'dict2', 'd': 'dict2', 'e': 'dict2'}

dict3 = dict1.copy()
dict3 = dict3 | dict2
dict4 = dict1.copy()
dict4 |= dict2
print(f'dict1:\n {dict1}')
print(f'dict2:\n {dict2}')
print(f'dict1 after dict1 = dict1 | dict2 (dict2 index c replaces dict1 index c, items in dict1 are discarded if present in dict2):\n {dict3}')
print(f'dict1 after dict1 |= dict2 (same behaviour as dict1 = dict1 | dict2):\n {dict4}')

dict5 = dict1.copy()
dict5 = dict2 | dict5
dict6 = dict2.copy()
dict6 |= dict1
print(f'dict1 after dict1 = dict2 | dict1 (dict2 index c is missing, dict1 index c was retained, items in dict2 are discarded if present in dict1):\n {dict5}')
print(f'dict2 after dict2 |= dict1 (same behaviour as dict2 = dict2 | dict1):\n {dict6}')


dict1:
 {'a': 'dict1', 'b': 'dict1', 'c': 'dict1'}
dict2:
 {'c': 'dict2', 'd': 'dict2', 'e': 'dict2'}
dict1 after dict1 = dict1 | dict2 (dict2 index c replaces dict1 index c, items in dict1 are discarded if present in dict2):
 {'a': 'dict1', 'b': 'dict1', 'c': 'dict2', 'd': 'dict2', 'e': 'dict2'}
dict1 after dict1 |= dict2 (same behaviour as dict1 = dict1 | dict2):
 {'a': 'dict1', 'b': 'dict1', 'c': 'dict2', 'd': 'dict2', 'e': 'dict2'}
dict1 after dict1 = dict2 | dict1 (dict2 index c is missing, dict1 index c was retained, items in dict2 are discarded if present in dict1):
 {'c': 'dict1', 'd': 'dict2', 'e': 'dict2', 'a': 'dict1', 'b': 'dict1'}
dict2 after dict2 |= dict1 (same behaviour as dict2 = dict2 | dict1):
 {'c': 'dict1', 'd': 'dict2', 'e': 'dict2', 'a': 'dict1', 'b': 'dict1'}