Python forward reference

That is, the function call precedes the function definition

Can do this

def BBB ():    print (' This is B ')    aaa () def aaa ():    print (' The ' a ') BBB ()--------->this is bthis a

Can do this

def aaa ():    print (' This was a ') def BBB ():    print (' This is B ')    aaa () BBB ()----------->this are bthis is a

But you can't do that.

def BBB ():    print (' This is B ')    aaa () BBB () def aaa ():    print ("This is a")--------->traceback (most recent Call last): The IS-b  file "e:/pycharm/test.py", line +, in <module>    BBB ()  file "e:/pycharm/ test.py ", line 599, in BBB    aaa () Nameerror:name ' AAA ' are not defined

　　

Python forward reference