python: global v.s. nonlocal

• Nonlocal
  Nonlocal is similar in meaning to global. But it takes effect primarily in nested methods. It means "not a global or local variable." So it changes the identifier to refer to an enclosing method's variable.

相关栗子阅读：

• global, nonlocal
• stackoverflow 上的问题: Python nonlocal statement

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PEP 3104 -- Access to Names in Outer Scopes