Python – Grouped Consecutive Range Indices of Elements

When it is required to get the grouped consecutive range of indices of elements in a list, a defaultdict is created. A simple iteration, along with ‘groupby’ method, ‘len’ method, ‘list’ method and the ‘append’ methods are used.

Example

Below is a demonstration of the same −

from itertools import groupby
from collections import defaultdict

my_list = [63, 12, 84, 91, 52, 39, 25, 27, 20, 11, 0,9]

print("The list is : " )
print(my_list)

my_index = 0
my_result = defaultdict(list)

for key, sub in groupby(my_list):
   element = len(list(sub))
   my_result[key].append((my_index, my_index + element - 1))
   my_index += element

print("The resultant dictionary is : ")
print(my_result)

Output

The list is :
[63, 12, 84, 91, 52, 39, 25, 27, 20, 11, 0, 9]
The resultant dictionary is :
defaultdict(, {63: [(0, 0)], 12: [(1, 1)], 84: [(2, 2)], 91: [(3, 3)], 52: [(4, 4)], 39: [(5, 5)], 25:
[(6, 6)], 27: [(7, 7)], 20: [(8, 8)], 11: [(9, 9)], 0: [(10, 10)], 9: [(11, 11)]})

Explanation

• The required packages are imported into the environment.

• A list of integers is defined and is displayed on the console.

• A value is initialized to 0.

• A default dictionary is created.

• The list is iterated over by applying the ‘groupby’ method on it.

• The initialized value is appended to the empty dictionary.

• This is displayed as the output on the console.