python中的全局和局部范围 [英] Global and local scope in python

问题描述

关于python中局部和全局作用域的初学者问题

Just a beginner question about local and global scope in python

X = 100
#is X a global variable?.We defined it outside the function scope
def foo():
    print(X)
    return X
#it prints 100 and even returns it
def foo():
    X = X + 10
#local error
#UnboundLocalError: local variable 'X' referenced before assignment
def foo():
    global X
    # if X is a global variable why specify again?
    X = X + 10
    return X

推荐答案

要修改变量的全局副本，您需要使用 global 关键字，但不需要 global 如果你只是访问那个.

To modify global copy of a variable you need the to use the global keyword, but you don't need global if you are only accessing that.

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