Python: Create a list reflecting the run-length encoding from a list

Last update on April 19 2025 12:59:10 (UTC/GMT +8 hours)

Create Run-Length Encoded List

Run-length encoding (RLE) is a form of lossless data compression in which runs of data (sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run.

Write a Python program to create a list reflecting the run-length encoding from a given list of integers or a given list of characters.

Sample Solution:

Python Code:

# Import the 'groupby' function from the 'itertools' module
from itertools import groupby

# Define a function 'encode_list' that takes a list 's_list' as input
def encode_list(s_list):
    # Use 'groupby' to group consecutive elements and count their occurrences
    return [[len(list(group)), key] for key, group in groupby(s_list)]

# Define a list 'n_list' with various elements including duplicates
n_list = [1, 1, 2, 3, 4, 4.3, 5, 1]

# Print a message indicating the purpose of the following output
print("Original list:") 

# Print the original list 'n_list'
print(n_list)

# Print a message indicating the purpose of the following output
print("\nList reflecting the run-length encoding from the said list:")

# Call the 'encode_list' function with 'n_list' as an argument and print the result of run-length encoding
print(encode_list(n_list))

# Reassign 'n_list' with a string
n_list = 'automatically'

# Print a message indicating the purpose of the following output
print("\nOriginal String:") 

# Print the original string 'n_list'
print(n_list)

# Print a message indicating the purpose of the following output
print("\nList reflecting the run-length encoding from the said string:")

# Call the 'encode_list' function with 'n_list' as an argument and print the result of run-length encoding for the string
print(encode_list(n_list))

Sample Output:

Original list:
[1, 1, 2, 3, 4, 4.3, 5, 1]

List reflecting the run-length encoding from the said list:
[[2, 1], [1, 2], [1, 3], [1, 4], [1, 4.3], [1, 5], [1, 1]]

Original String:
automatically

List reflecting the run-length encoding from the said string:
[[1, 'a'], [1, 'u'], [1, 't'], [1, 'o'], [1, 'm'], [1, 'a'], [1, 't'], [1, 'i'], [1, 'c'], [1, 'a'], [2, 'l'], [1, 'y']]

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to implement run-length encoding for a string.
Write a Python program to decode a run-length encoded list back to the original list.
Write a Python program to perform run-length encoding, but group elements into tuples.
Write a Python program to find the most frequently occurring element using run-length encoding.

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