global

定義「全局變數」：使在function區塊中定義的區域變數可以在整個程式中使用

>>>x = 6
>>>def func():
>>> global x
>>> x = 1
>>>
>>>func()
>>>print x
1

The keyword global is only useful to change or create global variables in a local context, although creating global variables is seldom considered a good solution.

>>>def bob():
>>>    me = "locally defined"    
>>> 　　# Defined only in local context
>>>    print me

>>>bob()
>>>print me     
>>># Asking for a global variable
locally defined
Traceback (most recent call last):
  File "file.py", line 9, in <module>
    print me
NameError: name 'me' is not defined

While if you use the global statement, the variable will become available "outside" the scope of the function, effectively becoming a global variable.

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在function區去中宣告global變數，執行該function之後，即可於function之外讀取該global變數

>>>def bob():
>>>    global me
>>>    me = "locally defined"   
>>>    # Defined locally but declared as global
>>>    print me

>>>bob()
>>>print me     
>>># Asking for a global variable
locally defined
locally defined