Python isalpha is buggy

This code

#!/usr/bin/env python
# -*- coding: utf-8 -*-
ml_string=u"സന്തോഷ്  हिन्दी"
for ch in ml_string:
    if(ch.isalpha()):
        print ch

gives this output

സ
ന
ത
ഷ
ह
न
द

And fails for all mathra signs of Indian languages. This is a known bug in glibc.

Does anybody know whether python internally use glibc functions for this basic string operations or use separate character database llke QT does?