Detailed explanation of Python function nesting

The Python language allows when defining a function, its function body contains the complete definition of another function. This is what we usually call nested definition.

Instance 1:

def OutFun():         #定义函数OutFun()，
    m=3               #定义变量m=3;
    def InFun():      #在OutFun内定义函数InFun()
        n=4           #定义局部变量n=4
        print m+n     #m相当于函数InFun()的全局变量
     InFun()          #OutFun()函数内调用函数InFun()

Instance 2:

def InFun(m):
    n=4
    print m+n
def OutFun()
     m=4
     InFun(m)

Instance 2 first defines the function InFun(), and then defines the OutFun() function again. At this time, InFun() and OutFun() are completely independent For the two functions, InFun() is called again within the OutFun() function; in fact, the nesting effect in instance 1 and instance 2 is the same, but in two different forms of expression.