iterate over a list of lists with another list in python

Question

I am wondering if I can iterate over a list of lists with another list in python:

let's say

lst_a = [x,y,z]  
lst_b = [[a,b,c,d],[e,f,g,h],[i,j,k,l]] 

where len(lst_a) = len(lst_b)

I am wondering how to get a new list like below:

lst_c = [[x/a, x/b, x/c, x/d],[y/e, y/f, y/g, y/h],[z/i, z/j, z/k, z/l]]

thanks a lot!

tim

Answer 1

You can use a nested list comprehension

>>> lst_a = [1,2,3]
>>> lst_b = [[1,2,3,4],[2,3,4,5],[3,4,5,6]]
>>> lst_c = [[i/b for b in j] for i,j in zip(lst_a, lst_b)]
>>> lst_c
[[1.0, 0.5, 0.3333333333333333, 0.25], [1.0, 0.6666666666666666, 0.5, 0.4], [1.0, 0.75, 0.6, 0.5]]

Answer 2

lst_a = [x,y,z]  
lst_b = [[a,b,c,d],[e,f,g,h],[i,j,k,l]] 
lst_c = []

for i in range(len(lst_a)):
    lst_c.append([lst_a[i]/lst_b[i][0]])
    for j in range(1, len(lst_b[i])):
        lst_c[i].append(lst_a[i]/lst_b[i][j])

Answer 3

You can do this using numpy.

import numpy

lst_a = [x,y,z]  
lst_b = [[a,b,c,d],[e,f,g,h],[i,j,k,l]] 
new_list = []

for i, item in enumerate(lst_a):
   new_list_i = float(lst_a[i])/numpy.array(lst_b[i])
   new_list.append(new_list_i.tolist())

print new_list