In Python, how can I find the index of the first item in a list that is NOT some value?

Question

Python\'s list type has an index(x) method. It takes a single parameter x, and returns the (integer) index of the first item in the list that has the value x.

Basica

Answer 1

Using a list comprehension when you only need the first just feels slimy (to me). Use a for-loop and exit early.

>>> lst = [None, None, None, "foo", None]
>>> for i, item in enumerate(lst):
...   if item: break
... else:
...   print "not found"
... 
>>> i
3