Question

Given the array a = [1,1,12,3,5,8,13,21] I can slice off the first 3 elements like a[:3] giving [1,1,2]. What I want is to slice off up to the element of vlaue i (e.g. if i=8 I want [1,1,12,3,5,8] or [1,1,12,3,5] (I can work with either)).

This works:

return a[:a.index(i)]

but only if I give it a value that’s in the array.

Is there a clean built in way to do this that does something sane on the missing value case?

Answer 1

1. That’s a list.

2. Try

   >>> a = [1,1,2,3,5,8,13,21]
   >>> import itertools
   >>> for x in itertools.takewhile(lambda val: val != 8, a):
   ...     print x
   ...
   1
   1
   2
   3
   5