python中的内嵌函数

1、

>>> def a():
    print("fun a is running!")
    def b():
        print("fun b is running!")
    b()

    
>>> a()         ## 示例中函数b是函数a的内嵌函数
fun a is running!
fun b is running!

>>> b()      ## 内嵌函数只能在函数内部调用
Traceback (most recent call last):
  File "<pyshell#719>", line 1, in <module>
    b()
NameError: name 'b' is not defined

2、

>>> def a():
    x = 100
    def b():
        print("x = ",x)
    b()

    
>>> a()      ## 内嵌函数可以调用外层函数的变量
x =  100

3、

>>> x = 500
>>> def a():
    x = 100
    def b():
        x = 10
        print("x = ", x)
    b()

    
>>> a()        ## 此种清空，函数调用自身定义的变量
x =  10

4、

>>> x = 500
>>> id(x)
2137596545936
>>> def a():
    x = 100
    print(id(x))
    def b():
        x = 10
        print(id(x))
    b()

    
>>> a()
140731529356032
140731529353152
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