Is there any way to say ignore case with "in"?

["Martin v. Löwis"]

>> I know I could use:-
>>
>>     if lower(string1) in lower(string2):
>>         <do something>
>>
>> but it somehow feels there ought to be an easier (tidier?) way.
>>
> 
> Easier?  You mean like some kind of mind meld?

Interestingly enough, it shouldn't be (but apparently is) obvious that

   a.lower() in b.lower()

is a way of expressing "a is a substring of b, with case-insensitive
matching". Can we be sure that these are really the same concepts,
and if so, is

  a.upper() in b.upper()

also equivalent?

It's probably a common assumption that, for any character c,
c.lower()==c.upper().lower(). Yet,

py> [i for i in range(65536) if unichr(i).upper().lower() !=
unichr(i).lower()]
[181, 305, 383, 837, 962, 976, 977, 981, 982, 1008, 1009, 1010, 1013,
7835, 8126]

Take, for example, U+017F, LATIN SMALL LETTER LONG S. It's .lower() is
the same character, as the character is already in lower case.
It's .upper() is U+0053, LATIN CAPITAL LETTER S. Notice that the LONG
is gone - there is no upper-case version of a "long s".
It's .upper().lower() is U+0073, LATIN SMALL LETTER S.

So should case-insensitive matching match the small s with the small
long s, as they have the same upper-case letter?

Regards,
Martin