Determinig position of a element in a list

Pedro Werneck pedro.werneck at
Mon Aug 25 22:20:53 CEST 2003

On Tue, 26 Aug 2003 00:29:04 +0200
"Przemo Drochomirecki" <pedrosch at> wrote:

> i can implement function index (e.x. index(5,A) = -1, index(7,A) = 2),
> but maybe there's is simpler(builtin?) solution

I have a strange feeling that I misunderstood your question,
because the list.index() builtin is pretty obvious:

list.index(value, [start, [stop]])

If this is what you want, maybe you can use something like this:

def index(value, lst):
        i = list.index(lst, value)
        return i
    except ValueError:
        return -1

a = [1,3,7,11,14,15]

assert index(3, a) == 1
assert index(12, a) == -1

or maybe:

class Ilist(list):
    def index(self, *args):
            i = list.index(self, *args)
            return i
        except ValueError:
            return -1

a = Ilist([1,3,7,11,14,15])

assert a.index(3) == 1
assert a.index(12) == -1



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