Python – Consecutive Repetition of Characters

Sometimes, while working with character lists we can have a problem in which we need to perform consecutive repetition of characters. This can have application in many domains. Lets discuss certain ways in which this task can be performed.

Method #1 : Using list comprehension
This is one of the way in which this task can be performed. In this, we perform a brute force way to perform but in a one-liner for by multiplying each character by magnitude.

# Python3 code to demonstrate working of
# Consecutive Repetition of  Characters
# Using list comprehension

# initializing list
test_list = ['g', 'f', 'g', 'i', 's', 'b', 'e', 's', 't']

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

# initializing K
K = 3

# Consecutive Repetition of  Characters
# Using list comprehension
res = [sub for ele in test_list for sub in [ele] * K]

# printing result
print("The list after Consecutive Repetition is : " + str(res))

Output :

The original list is : [‘g’, ‘f’, ‘g’, ‘i’, ‘s’, ‘b’, ‘e’, ‘s’, ‘t’]
The list after Consecutive Repetition is : [‘g’, ‘g’, ‘g’, ‘f’, ‘f’, ‘f’, ‘g’, ‘g’, ‘g’, ‘i’, ‘i’, ‘i’, ‘s’, ‘s’, ‘s’, ‘b’, ‘b’, ‘b’, ‘e’, ‘e’, ‘e’, ‘s’, ‘s’, ‘s’, ‘t’, ‘t’, ‘t’]

Method #2 : Using chain() + repeat()
The combination of above functions can be used to solve this problem. In this, we perform the task of repeating using repeat() and the result construction using chain().

# Python3 code to demonstrate working of
# Consecutive Repetition of  Characters
# Using chain() + repeat()
from itertools import chain, repeat

# initializing list
test_list = ['g', 'f', 'g', 'i', 's', 'b', 'e', 's', 't']

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

# initializing K
K = 3

# Consecutive Repetition of  Characters
# Using chain() + repeat()
res = list(chain.from_iterable(repeat(chr, K) for chr in test_list))

# printing result
print("The list after Consecutive Repetition is : " + str(res))

Output :

The original list is : [‘g’, ‘f’, ‘g’, ‘i’, ‘s’, ‘b’, ‘e’, ‘s’, ‘t’]
The list after Consecutive Repetition is : [‘g’, ‘g’, ‘g’, ‘f’, ‘f’, ‘f’, ‘g’, ‘g’, ‘g’, ‘i’, ‘i’, ‘i’, ‘s’, ‘s’, ‘s’, ‘b’, ‘b’, ‘b’, ‘e’, ‘e’, ‘e’, ‘s’, ‘s’, ‘s’, ‘t’, ‘t’, ‘t’]