Looking for a pythonic way to sum values from multiple lists: I have got the following list of lists:
a = [0,5,2]
b = [2,1,1]
c = [1,1,1]
d = [5,3,4]
my_list = [a,b,c,d]
I am looking for the output:
[8,10,8]
I`ve used:
print ([sum(x) for x in zip(*my_list )])
but zip only works when I have 2 elements in my_list. Any idea?
zip works for an arbitrary number of iterables:
>>> list(map(sum, zip(*my_list)))
[8, 10, 8]
which is, of course, roughly equivalent to your comprehension which also works:
>>> [sum(x) for x in zip(*my_list)]
[8, 10, 8]
Numpy has a nice way of doing this, it is also able to handle very large arrays. First we create the my_list as a numpy array as such:
import numpy as np
a = [0,5,2]
b = [2,1,1]
c = [1,1,1]
d = [5,3,4]
my_list = np.array([a,b,c,d])
To get the sum over the columns, you can do the following
np.sum(my_list, axis=0)
Alternatively, the sum over the rows can be retrieved by
np.sum(my_list, axis=1)
I'd make it a numpy array and then sum along axis 0:
my_list = numpy.array([a,b,c,d])
my_list.sum(axis=0)
Output:
[ 8 10 8]
