when comparing two strings in python, it works fine and when comparing a string object with a unicode object it fails as expected however when comparing a string object with a converted unicode (unicode --> str) object it fails

A Demo:

Works as expected:

>>> if 's' is 's': print "Hurrah!"
... 
Hurrah!

Pretty much yeah:

>>> if 's' is u's': print "Hurrah!"
... 

Not expected:

>>> if 's' is str(u's'): print "Hurrah!"
... 

Why doesn't the third example work as expected when both the type's are of the same class?

>>> type('s')
<type 'str'>

>>> type(str(u's'))
<type 'str'>