About variable scopes for Python

#定义变量a >>> A = 0>>> print a0 #定义函数p () >>> def p ():     ... Print a ...     >>> p () 0 #定义函数p2 () >>> def p2 ():     ... Print a ...     A = 3     ... Print a ...     >>> P2 () # Run error, external variable A is referenced first, cannot be re-assigned Traceback (most recent called last):  File ' <interactive input> ', line 1, In <module>  File "<interactive input>", Line 2, in p2unboundlocalerror:local variable ' a ' referenced bef Ore assignment #定义函数p3 () >>> def P3 ():     ... A = 3 # does not refer to direct assignment     ... Print a ...     >>> P3 () 3>>> Print A0 # External variable A does not change

　　

About variable scopes for Python