I have now:
list1 = [1, 2, 3]
list2 = [4, 5, 6]
I wish to have:
[1, 2, 3]
+ + +
[4, 5, 6]
|| || ||
[5, 7, 9]
Simply an element-wise addition of two lists.
I can surely iterate the two lists, but I don't want do that.
What is the most Pythonic way of doing so?
Use map
with operator.add
:
>>> from operator import add
>>> list( map(add, list1, list2) )
[5, 7, 9]
or zip
with a list comprehension:
>>> [sum(x) for x in zip(list1, list2)]
[5, 7, 9]
>>> list2 = [4, 5, 6]*10**5
>>> list1 = [1, 2, 3]*10**5
>>> %timeit from operator import add;map(add, list1, list2)
10 loops, best of 3: 44.6 ms per loop
>>> %timeit from itertools import izip; [a + b for a, b in izip(list1, list2)]
10 loops, best of 3: 71 ms per loop
>>> %timeit [a + b for a, b in zip(list1, list2)]
10 loops, best of 3: 112 ms per loop
>>> %timeit from itertools import izip;[sum(x) for x in izip(list1, list2)]
1 loops, best of 3: 139 ms per loop
>>> %timeit [sum(x) for x in zip(list1, list2)]
1 loops, best of 3: 177 ms per loop