使用+ =而不是附加列表时出现UnboundLocalError | 而不是附加列表时出现UnboundLocalError

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问题描述

我不太了解以下两个相似代码之间的区别:

I do not quite understand the difference between the following two similar codes:

def y(x):
    temp=[]
    def z(j):
        temp.append(j)
    z(1)
    return temp

调用y(2)返回[1]

def y(x):
    temp=[]
    def z(j):
        temp+=[j]
    z(1)
    return temp

调用y(2)返回UnboundLocalError: local variable 'temp' referenced before assignment.为什么+运算符会生成错误?谢谢

calling y(2) returns UnboundLocalError: local variable 'temp' referenced before assignment. Why + operator generates the error? Thanks

推荐答案

标题，+和"append"之间的区别是:

Answer to the heading, the difference between + and "append" is:

[11, 22] + [33, 44,]

会给您:

[11, 22, 33, 44]

和.

b = [11, 22, 33]
b.append([44, 55, 66])

会给你

[11, 22, 33 [44, 55, 66]]

回答错误

这里的问题是temp+=[j]等于temp = temp +[j].在分配变量之前，先在此处读取temp变量.这就是为什么它会导致此问题.实际上，这在python FAQ中已涉及.

The problem here is temp+=[j] is equal to temp = temp +[j]. The temp variable is read here before its assigned. This is why it's giving this problem. This is actually covered in python FAQ's.

有关更多信息，请点击此处. :)

For further readings, click here. :)

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