>>> s="I am fine"
>>> s
'I am fine'
>>> s.split(" ")
['I', 'am', 'fine']
>>> sList=s.split(" ")
>>> sList
['I', 'am', 'fine']
>>> "%".join(sList)
'I%am%fine'
Notes:
1)String is transfered to a List by split method
2)List can be joined a string by join method