I have a Python script which takes as input a list of integers, which I need to work with four integers at a time. Unfortunately, I don't have control of the input, or I'd have it passed in as a list of four-element tuples. Currently, I'm iterating over it this way:
for i in xrange(0, len(ints), 4):
# dummy op for example code
foo += ints[i] * ints[i + 1] + ints[i + 2] * ints[i + 3]
It looks a lot like "C-think", though, which makes me suspect there's a more pythonic way of dealing with this situation. The list is discarded after iterating, so it needn't be preserved. Perhaps something like this would be better?
while ints:
foo += ints[0] * ints[1] + ints[2] * ints[3]
ints[0:4] = []
Still doesn't quite "feel" right, though. :-/
Related question: How do you split a list into evenly sized chunks in Python?
I'm a fan of
If the list is large, the highest-performing way to do this will be to use a generator:
Posting this as an answer since I cannot comment...
Using map() instead of zip() fixes the padding issue in J.F. Sebastian's answer:
Example:
With NumPy it's simple:
output:
You can use partition or chunks function from funcy library:
These functions also has iterator versions
ipartition
andichunks
, which will be more efficient in this case.You can also peek at their implementation.