Python regex partially case insensitive

Question

How to do it in nice short way? I have 2 strings and I want to search one in another, but:

• lowercase letter matches to lower- and uppercase
• uppercase letter matches only to uppercase.

Example:

"abcd" matches to "AbCd", "ABCD", or "abcd"

"Abcd" matches to "Abcd", "ABcd" and so on, but not matches to "abcd"

Answer 1

You need to transform your regular expressions, something like

def transform(regex):
    return ''.join([
        "[%s%s]" % (c, c.upper())
            if c.islower()
            else c
        for c in regex
    ])


transformed = transform('Abcd')

Will transform the regex Abcd into A[bB][cC][dD].

Of course this does not work, if your actual regex does have character classes [a-z] already.