Python正则表达式；替换匹配的一部分 [英] Python Regular Expression; replacing a portion of match

问题描述

如何限制匹配/替换 e004_n07 中的前导零?但是，如果任一术语包含全零，那么我需要在该术语中保留一个零(请参见下面的示例).对于输入字符串，第一个值总是有 3 位数字，第二个值总是有 2 位数字.

How would I limit match/replacement the leading zeros in e004_n07? However, if either term contains all zeros, then I need to retain one zero in the term (see example below). For the input string, there will always be 3 digits in the first value and 2 digits in the second value.

示例输入和输出

e004_n07 #e4_n7
e020_n50 #e20_n50
e000_n00 #e0_n0

这可以单独使用 re.sub 来完成，还是需要使用 re.search/re.match?

Can this be accomplished with re.sub alone, or do I need to use re.search/re.match?

推荐答案

如果只想去掉字母后的零，可以使用:

If you want to only remove zeros after letters, you may use:

([a-zA-Z])0+

替换为 \1 反向引用.请参阅正则表达式演示.

Replace with \1 backreference. See the regex demo.

([a-zA-Z]) 将捕获一个字母，0+ 将匹配 1 个或多个零.

The ([a-zA-Z]) will capture a letter and 0+ will match 1 or more zeros.

Python 演示:

import re
s = 'e004_n07'
res = re.sub(r'([a-zA-Z])0+', r'\1', s)
print(res)

请注意，re.sub 将查找并替换所有不重叠的匹配项(将执行全​​局搜索和替换).如果没有匹配项，字符串将按原样返回，无需修改.因此，无需使用额外的 re.match/re.search.

Note that re.sub will find and replace all non-overlapping matches (will perform a global search and replace). If there is no match, the string will be returned as is, without modifications. So, there is no need using additional re.match/re.search.

UDPATE

如果数字只包含零，要保留 1 个零，您可以使用

To keep 1 zero if the numbers only contain zeros, you may use

import re
s = ['e004_n07','e000_n00']
res = [re.sub(r'(?<=[a-zA-Z])0+(\d*)', lambda m: m.group(1) if m.group(1) else '0', x) for x in s]
print(res)

查看 Python 演示

这里，r'(?<=[a-zA-Z])0+(\d*)' 正则表达式匹配一个或多个零 (0+) 在一个 ASCII 字母 ((?<=[a-zA-Z])) 之后，然后任何其他数字(0 或更多)被捕获到组 1 中，(\d*).然后，在替换中，我们检查Group 1是否为空，如果为空，我们插入0(只有零)，否则插入Group 1的内容(后面的剩余数字)第一个前导零).

Here, r'(?<=[a-zA-Z])0+(\d*)' regex matches one or more zeros (0+) that are after an ASCII letter ((?<=[a-zA-Z])) and then any other digits (0 or more) are captured into Group 1 with (\d*). Then, in the replacement, we check if Group 1 is empty, and if it is empty, we insert 0 (there are only zeros), else, we insert Group 1 contents (the remaining digits after the first leading zeros).

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