I am trying to find a substring with this pattern: .*(_\d+)?
我试图找到这种模式的子串:。*(_ \ d +)?
Example:
abc_4
abc_345
abc
Just one regular string, followed by an optional "_", followed by at least one digit.
只有一个常规字符串,后跟一个可选的“_”,后跟至少一个数字。
But when I use:
但是当我使用时:
re.search("(.*)(_\d+)?" , str).group(1)
it always returns the entire string.
它总是返回整个字符串。
3 个解决方案
#1
0
The problem is that * is greedy, it tries to match the longest possible string, so long as the rest of the regexp can match. Since the part after _ is optional, .* can gobble it up, since the rest of the regexp can match an empty string.
问题是*是贪婪的,它试图匹配最长的字符串,只要正则表达式的其余部分可以匹配。由于_之后的部分是可选的,因此。*可以吞噬它,因为正则表达式的其余部分可以匹配空字符串。
Change .* to [^_]* so that it can't match the underscore before the number.
将。*更改为[^ _] *,使其与数字前的下划线不匹配。
([^]*)(_\d+)?
#2
1
instead of (.*) use [^_]*? to stop at the first _ character.
而不是(。*)使用[^ _] *?停在第一个_字符处。
#3
1
You have made the _nnn part optional (?), so the .* is matching the whole string always (greedy). Make it non-greedy:
你已经使_nnn部分成为可选(?),所以。*总是匹配整个字符串(贪婪)。让它不贪心:
.*?(_\d+)?
#1
0
The problem is that * is greedy, it tries to match the longest possible string, so long as the rest of the regexp can match. Since the part after _ is optional, .* can gobble it up, since the rest of the regexp can match an empty string.
问题是*是贪婪的,它试图匹配最长的字符串,只要正则表达式的其余部分可以匹配。由于_之后的部分是可选的,因此。*可以吞噬它,因为正则表达式的其余部分可以匹配空字符串。
Change .* to [^_]* so that it can't match the underscore before the number.
将。*更改为[^ _] *,使其与数字前的下划线不匹配。
([^]*)(_\d+)?
#2
1
instead of (.*) use [^_]*? to stop at the first _ character.
而不是(。*)使用[^ _] *?停在第一个_字符处。
#3
1
You have made the _nnn part optional (?), so the .* is matching the whole string always (greedy). Make it non-greedy:
你已经使_nnn部分成为可选(?),所以。*总是匹配整个字符串(贪婪)。让它不贪心:
.*?(_\d+)?