变量范围(Python 新手) [英] Variable scope (Python Newbie)

问题描述

我在功能块内的全局列表上使用 .pop 方法，但全局列表正在块外更新.我认为局部变量不能修改全局变量.

I am using a .pop method on a Global list inside a function block, but the Global list is being updated outside the block. I thought that local variables can't modify Global variables.

这不应该工作，但确实有效:

This should not work, but it does:

import random

PhraseBank = ['a','b','c','d']

def getPuzzle(secretphrase):
    phraseIndex = random.randint(0,len(PhraseBank)-1)
    secretphrase = PhraseBank.pop(phraseIndex)
    return secretphrase #Returns and item indexed from the PhraseBank

while len(PhraseBank) != 0:
    secretphrase = getPuzzle(PhraseBank) #works
    print(secretphrase, PhraseBank)

输出为:

a ['b', 'c', 'd']
d ['b', 'c']
c ['b']
b []

为什么我只在功能块内修改 PhraseBank 会在全局范围内更新?

Why is PhraseBank getting updated Globally when I am only modifying it inside a function block?

推荐答案

你不能赋值给一个函数内的全局变量(除非你明确使用一个global宣言).您可以很好地修改存储在全局变量中的对象.

You can't assign to a global variable inside a function (unless you explicitly use a global declaration). You can modify objects stored in global variables just fine.

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