s = www.edureka.in
print s.strip(string.lowercase)
Output - .edureka.
It is because strip function removes the mentioned leading and training values and not from in-between the string. In this case lowercase letters were supposed to be removed.
Hence it removed the leading lowercase letters before it encounters a non-lowercase character i.e. ' . ' in this case. Similarly it removes all the trailing lowercase letter from the end till it encounter ' . ' i.e. a non-lowercase character.
To make it more easier to understand lets replace . with a capital letter and execute the code again.
s = wwwRedurekaRin
print s.strip(string.lowercase)
Output - RedurekaR
It removes all the lowercase letters from the start and the end till it encounters a capital letter on both sides.