Python index of item in list without error? [duplicate]

Question

To find the index of an item in a list, you use:

list.index(x) Return the index in the list of the first item whose value is x.  It is an error if there is no such item. 

That seems a little odd to me, that it would throw an error if the item wasn't found. Where I come from (Objective-C land), it returns a NSNotFound enum (which is just a max int, indicating the item wasn't found).

So I made something ugly to go around this:

index = 0 for item in self.items:    if item.id == desired_id:         return index     index = index + 1  return -1 

I used -1 to indicate the item wasn't found. What's a better way to do this, and why doesn't Python have something like this built in?

Answer 1

a = [1] try:     index_value = a.index(44) except ValueError:     index_value = -1 

How about this?

Answer 2

It's not a good idea to return -1 as that is a valid index in Python (see Python list.index throws exception when index not found).

Probably best to catch the index error and act accordingly.