用双引号或单引号引起来的正则表达式字符串

Question

I got this regex:

(\s|'|\")((?=.*[0-9])(?=.*[a-zA-Z]))([a-z0-9]{8})(\s|'|\")

to search for strings of length 8 having one lower case character and one digit. The string needs to be enclosed by space, quote or double quote.

What does not work in the expression: something like this would be accepted: "1234567a' . If string starts with ' it should end with ' , when starting with " it should end by " etc.

I am not very strong at regexes so let me ask if there is a better way to enforce same character for begin and end without repeating regex 3 times?

Answer 1

If you want to match the same char at the end of the string as the one at its start, you may use a backreference to the char once it is captured into a capturing group.

Besides, to make sure you match at the start of the string, add ^ anchor at the start of the string and $ anchor at the end of string:

r'''^([\s'"])(?=.*[0-9])(?=.*[a-zA-Z])[a-zA-Z0-9]{8}\1$'''

See the regex demo

The ([\\s'"]) is a capturing group with ID 1, so, the \\1 backreference at the end matches the same text as is stored in Group 1 memory buffer.