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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 range(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?
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The best way to iterate the list in terms of performance would be to use iterators ( your second approach using foreach ).
Iterating over a List is much much faster than iterating over a set. The currently accepted answer is using a very small set and list and hence, the difference is negligible there.
💡 Python's “for” loops are “for-each” loops I would consider this solution to be quite Pythonic. It's nice and clean and almost reads like pseudo code from a text book. I don't have to keep track of the container's size or a running index to access elements.
def chunker(seq, size): return (seq[pos:pos + size] for pos in range(0, len(seq), size)) # (in python 2 use xrange() instead of range() to avoid allocating a list) Works with any sequence:
text = "I am a very, very helpful text" for group in chunker(text, 7): print(repr(group),) # 'I am a ' 'very, v' 'ery hel' 'pful te' 'xt' print '|'.join(chunker(text, 10)) # I am a ver|y, very he|lpful text animals = ['cat', 'dog', 'rabbit', 'duck', 'bird', 'cow', 'gnu', 'fish'] for group in chunker(animals, 3): print(group) # ['cat', 'dog', 'rabbit'] # ['duck', 'bird', 'cow'] # ['gnu', 'fish'] If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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