Getting elements in certain range of list

Question

I have a Python list, for example list = [1,2,3,4,5,6,7,8,9] . In addition, I have another list list2 = ['a','b','c','d','e','f','g','h','j'] . Now I would like to do the following:

idx = (list > 3) & (list < 7)
list2 = list2[idx]

This should yield ['d','e','f'] . Of course, this is not possible with lists. How can this be done with lists?

Answer 1

You can use zip :

l1 = [1,2,3,4,5,6,7,8,9]
l2 = ['a','b','c','d','e','f','g','h','j']
result = [a for a, b in zip(l2, l1) if 3 < b < 7]

Output:

['d', 'e', 'f']

To get the reduced list as well:

result, reduced = map(list, zip(*[[a, b] for a, b in zip(l2, l1) if 3 < b < 7]))

Output:

['d', 'e', 'f'] #result
[4, 5, 6] #reduced

Answer 2

Try this:

#Make sure all lists are numpy arrays.
import numpy as np
idx = np.where((list > 3) & (list < 7))
list2 = list2[idx]

Answer 3

Option with list comprehension accessing elements by index:

res = [ list2[idx] for idx, e in enumerate(list1) if 7 > e > 3 ]
print(res) #=> ['d', 'e', 'f']

---

To get the elements from both the lists:

res1, res2 = [ list(i) for i in zip(*[ [list2[idx], e] for idx, e in enumerate(list1) if 7 > e > 3 ]) ]
print (res1, res2 ) #=> ['d', 'e', 'f'] [4, 5, 6]

Then transpose:

 res1, res2 = [ list(i) for i in zip(*[ [list2[idx], e] for idx, e in enumerate(list1) if 7 > e > 3 ]) ] print (res1, res2 ) #=> ['d', 'e', 'f'] [4, 5, 6]