Python:替换字符串中除最后一个之外的术语 [英] Python: replace terms in a string except for the last

问题描述

如何替换字符串中的术语 - 除了最后一个，需要替换为不同的内容?

How does one go about replacing terms in a string - except for the last, which needs to be replaced to something different?

示例:

    letters = 'a;b;c;d'

需要改成

    letters = 'a, b, c & d'

我已经使用了替换功能，如下:

I have used the replace function, as below:

    letters = letters.replace(';',', ')

给予

    letters = 'a, b, c, d'

问题是我不知道如何将最后一个逗号替换为&符号.不能使用位置相关函数，因为可能有任意数量的字母，例如 'a;b' 或 'a;b;c;d;e;f;g' .我已经搜索过 stackoverflow 和 python 教程，但找不到一个函数来替换最后找到的术语，有人可以帮忙吗?

The problem is that I do not know how to replace the last comma from this into an ampersand. A position dependent function cannot be used as there could be any number of letters e.g 'a;b' or 'a;b;c;d;e;f;g' . I have searched through stackoverflow and the python tutorials, but cannot find a function to just replace the last found term, can anyone help?

推荐答案

在 str.replace 中，您还可以传递一个可选的第三个参数(count)，用于处理正在完成的替换次数.

In str.replace you can also pass an optional 3rd argument(count) which is used to handle the number of replacements being done.

In [20]: strs = 'a;b;c;d'

In [21]: count = strs.count(";") - 1

In [22]: strs = strs.replace(';', ', ', count).replace(';', ' & ')

In [24]: strs
Out[24]: 'a, b, c & d'

str.replace 的帮助:

S.replace(old, new[, count]) -> string

Return a copy of string S with all occurrences of substring
old replaced by new.  If the optional argument count is
given, only the first count occurrences are replaced.

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