How to strip a specific word from a string?

Easiest way would be to simply replace it with an empty string.

s = s.replace('papa', '')

Use str.replace.

>>> papa.replace('papa', '')
' is a good man'
>>> app.replace('papa', '')
'app is important'

Alternatively use re and use regular expressions. This will allow the removal of leading/trailing spaces.

>>> import re
>>> papa = 'papa is a good man'
>>> app = 'app is important'
>>> papa3 = 'papa is a papa, and papa'
>>>
>>> patt = re.compile('(\s*)papa(\s*)')
>>> patt.sub('\\1mama\\2', papa)
'mama is a good man'
>>> patt.sub('\\1mama\\2', papa3)
'mama is a mama, and mama'
>>> patt.sub('', papa3)
'is a, and'