UnboundLocalError: local variable ‘x‘ referenced before assignment 分析

[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] on linux
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>>> x=111
>>> def func():
...     x=222
...     print(x)
... 
>>> func()
222
>>> def func1():
...     print(x)
...     x=333
... 
>>> func1()
Traceback (most recent call last):
  File "", line 1, in
  File "", line 2, in func1
UnboundLocalError: local variable 'x' referenced before assignment
>>> def func2():
...     print(x)
... 
>>> func2()
111
>>> 

判断变量是全局变量还是局部变量，以定义阶段为准，func2没有报错是因为将变量识别为全局变量，func1报错是在运行阶段时的报错，是因为将变量识别为局部变量