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Python | Finding 'n' Character Words in a Text File

Last Updated : 12 Jul, 2025

This article aims to find words with a certain number of characters. In the code mentioned below, a Python program is given to find the words containing three characters in the text file.

Example

Input: Hello, how are you ? , n=3
Output: how are you
Explanation: Output contains every character of the of length 3 from the input file.

Input File: File1.txt

Below are the methods that we will cover in this article:

• Using Split and List Comprehension
• Using Regular Expressions
• Using Generator Function

You can read the file, split its content into words, and then filter out words with 'n' characters using list comprehension.

def find_words_with_three_chars(file_path):
    with open(file_path, 'r') as file:
        content = file.read()
        words = content.split()

        words_with_three_chars = [word for word in words if len(word) == 3]

        return words_with_three_chars

file_name = "File1.txt"
result = find_words_with_three_chars(file_name)

print("Words containing three characters:")
print(result)

Output:

Words containing three characters: ['sit', 'sed', 'sit', 'ac.', 'dui', 'sit']

Time Complexity: O(N), where N is the total number of characters in the file.
Space Complexity: O(N + M), where M is the number of words with 'n' characters in the file.

In Python, we have re module which provides regular expression functionality. The Regular expressions can be used to match patterns in the text which allows you to find words with 'n' characters.

import re

def find_n_character_words(file_path, n):
    with open(file_path, 'r') as file:
        content = file.read()

    # Use regular expression to find words with 'n' characters
    pattern = r'\b\w{' + str(n) + r'}\b'
    words_with_n_chars = re.findall(pattern, content)

    return words_with_n_chars

file_name = "File1.txt"
n = 3
result = find_n_character_words(file_name, n)

print(f"Words containing {n} characters:")
print(result)

Output:

Words containing 3 characters:
['sit', 'sed', 'sit', 'dui', 'sit']

Time Complexity: O(N), where N is the total number of characters in the file.
Space Complexity: O(N)

Here you can use a generator function to yield words with 'n' characters one by one. This can be useful for large files.

def generate_n_character_words(file_path, n):
    with open(file_path, 'r') as file:
        for line in file:
            for word in line.split():
                if len(word) == n:
                    yield word

file_name = "File1.txt"
n = 3
result_generator = generate_n_character_words(file_name, n)

print(f"Words containing {n} characters:")
for word in result_generator:
    print(word)

Output:

Words containing 3 characters:
sit
sed
sit
dui
sit

Time Complexity: O(N), where N is the total number of characters in the file.
Space Complexity: O(M), where M is the number of words with 'n' characters in the file.

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