“str"对象不支持项目分配 [英] 'str' object does not support item assignment

问题描述

我想从字符串 s1 中读取一些字符并将其放入另一个字符串 s2.

I would like to read some characters from a string s1 and put it into another string s2.

然而，赋值给 s2[j] 会报错:

However, assigning to s2[j] gives an error:

s2[j] = s1[i]

# TypeError: 'str' object does not support item assignment

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在 C 中，这是有效的:

---

In C, this works:

int i = j = 0;
while (s1[i] != '\0')
    s2[j++] = s1[i++];

我在 Python 中的尝试:

My attempt in Python:

s1 = "Hello World"
s2 = ""
j = 0

for i in range(len(s1)):
    s2[j] = s1[i]
    j = j + 1

推荐答案

在 Python 中，字符串是不可变的，因此您无法就地更改其字符.

In Python, strings are immutable, so you can't change their characters in-place.

但是，您可以执行以下操作:

You can, however, do the following:

for c in s1:
    s2 += c

这样做的原因是它是一个快捷方式:

The reasons this works is that it's a shortcut for:

for c in s1:
    s2 = s2 + c

上面的每次迭代都会创建一个新字符串，并将对该新字符串的引用存储在s2中.

The above creates a new string with each iteration, and stores the reference to that new string in s2.

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