Ignore case in Python strings [duplicate]

Answer 1

For occasional or even repeated comparisons, a few extra string objects shouldn't matter as long as this won't happen in the innermost loop of your core code or you don't have enough data to actually notice the performance impact. See if you do: doing things in a "stupid" way is much less stupid if you also do it less.

If you seriously want to keep comparing lots and lots of text case-insensitively you could somehow keep the lowercase versions of the strings at hand to avoid finalization and re-creation, or normalize the whole data set into lowercase. This of course depends on the size of the data set. If there are a relatively few needles and a large haystack, replacing the needles with compiled regexp objects is one solution. If It's hard to say without seeing a concrete example.

Answer 2

You could subclass str and create your own case-insenstive string class but IMHO that would be extremely unwise and create far more trouble than it's worth.

Answer 3

This question is asking 2 very different things:

1. What is the easiest way to compare strings in Python, ignoring case?
2. I guess I'm looking for an equivalent to C's stricmp().

Since #1 has been answered very well already (ie: str1.lower() < str2.lower()) I will answer #2.

def strincmp(str1, str2, numchars=None):
    result = 0
    len1 = len(str1)
    len2 = len(str2)
    if numchars is not None:
        minlen = min(len1,len2,numchars)
    else:
        minlen = min(len1,len2)
    #end if
    orda = ord('a')
    ordz = ord('z')

    i = 0
    while i < minlen and 0 == result:
        ord1 = ord(str1[i])
        ord2 = ord(str2[i])
        if ord1 >= orda and ord1 <= ordz:
            ord1 = ord1-32
        #end if
        if ord2 >= orda and ord2 <= ordz:
            ord2 = ord2-32
        #end if
        result = cmp(ord1, ord2)
        i += 1
    #end while

    if 0 == result and minlen != numchars:
        if len1 < len2:
            result = -1
        elif len2 < len1:
            result = 1
        #end if
    #end if

    return result
#end def

Only use this function when it makes sense to as in many instances the lowercase technique will be superior.

I only work with ascii strings, I'm not sure how this will behave with unicode.

Answer 4

import re
if re.match('tEXT', 'text', re.IGNORECASE):
    # is True