Question

程序从一个给定的字符串中获取一个字符串，其中所有出现的第一个字符都已更改为＆＃39; $＆＃39;，除了第一个字符本身。示例字符串：＆＃39;重启＆＃39; 预期结果：＆＃39; resta $ t＆＃39;

这是我的代码

    def change(string):
        string_len = len(string)
        t = string[0]
        for each in range(1, string_len):
            if each is t:
                each == '$'
            else:
                continue
    return string

print(change("restart"))

output
restart

我使用Pycharm。第6行（每个==＆＃39; $＆＃39;）表示此声明无效。我不想使用替换方法。只想知道是什么问题。

Answer 1

您的代码已评论：

    def change(string):
        string_len = len(string)
        t = string[0]
        for each in range(1, string_len):
            if each is t: # To compara strings you should use the == operator not the 'is' operator.
                each == '$' # This will not have any effect because is a temporal variable visible just inside the 'for' loop and you are not using it.
            else:
                continue
    return string

print(change("restart"))

解决方案可能是：

def change(s):
    result = ''
    for character in s:
        result += '$' if character == s[0] else character
    return result


print(change('restart'))

Python字符串是不可变对象，因此您无法'aaa'[1] = 'b'获取aba。

Answer 2

each设置为整数，您将其与字符串进行比较。

声明无效（Python）

2 个答案: