Use replace method of strings not strip:
s = s.replace(',','')
An example:
>>> s = 'Foo, bar'
>>> s.replace(',',' ')
'Foo bar'
>>> s.replace(',','')
'Foo bar'
>>> s.strip(',') # clears the ','s at the start and end of the string which there are none
'Foo, bar'
>>> s.strip(',') == s
True