It's possible to remove elements with the method remove() without knowing the corresponding indices.
s.remove(x)
This call removes the first occurence of the value x from the list s.
If x is not contained in the list, the following exeption is thrown:
„ValueError: list.remove(x): x not in list“
>>> colors=["red","green","blue","green","yellow"]
>>> colors.remove("green")
>>> colors
['red', 'blue', 'green', 'yellow']