Flatten Python lists with itertools module¶

Every now and then you end up with a data structure that looks like this:

listOflists = [[1,2,3],[4,5,6]]

Then you would like to 'flatten' this list to essentially loop over it as a single list instead of a list of 2 separate, smaller lists. Well, check out the itertools module for a good recipe on how to do this.

def flatten(listOfLists):
    "Flatten one level of nesting"
    return chain.from_iterable(listOfLists)