Python – Extract elements from Ranges in List

Given a list, and a list of tuples with ranges, extract all elements in those ranges from list.

Input : test_list = [4, 5, 4, 6, 7, 5, 4, 5, 6, 10], range_list = [(2, 4), (7, 8)]
Output : [4, 6, 7, 5, 6]
Explanation : 4, 6, 7 are elements at idx 2, 3, 4 and 5, 6 at idx 7, 8.

Input : test_list = [4, 5, 4, 6, 7, 5, 4, 5, 6, 10], range_list = [(2, 6)]
Output : [4, 6, 7, 5, 4]
Explanation : Elements from 2-6 index are extracted.

Method #1 : Using loop + list slicing 

In this, we extract each range using list slicing and using loop iterate for each range and keep extending the extracting slices to extending list.

Python3

# Python3 code to demonstrate working of
# Extract elements from Ranges in List
# Using loop + list slicing

# initializing list
test_list = [4, 5, 4, 6, 7, 5, 4, 5, 4, 6, 4, 6, 9, 8]

# printing original list
print("The original list is : " + str(test_list))

# initializing ranges
range_list = [(2, 4), (7, 8), (10, 12)]

res = []
for ele in range_list:

    # extending ranges
    res.extend(test_list[ele[0] : ele[1] + 1])

# printing result
print("Ranges elements : " + str(res))

Output

The original list is : [4, 5, 4, 6, 7, 5, 4, 5, 4, 6, 4, 6, 9, 8]
Ranges elements : [4, 6, 7, 5, 4, 4, 6, 9]

Method #2  : Using list comprehension

In this, we apply similar method as above function, difference being that list comprehension is used to solve this in compact form.

Python3

# Python3 code to demonstrate working of
# Extract elements from Ranges in List
# Using list comprehension
from itertools import chain

# initializing list
test_list = [4, 5, 4, 6, 7, 5, 4, 5, 4, 6, 4, 6, 9, 8]

# printing original list
print("The original list is : " + str(test_list))

# initializing ranges
range_list = [(2, 4), (7, 8), (10, 12)]

# using one-liner to solve this problem
res = list(chain.from_iterable([test_list[ele[0] : ele[1] + 1] for ele in range_list]))

# printing result
print("Ranges elements : " + str(res))

Output

The original list is : [4, 5, 4, 6, 7, 5, 4, 5, 4, 6, 4, 6, 9, 8]
Ranges elements : [4, 6, 7, 5, 4, 4, 6, 9]