How to Obtain the Line Number in which Given Word is Present using Python

Given a text file, find the line number where a specific word or phrase appears. Below is the Input File used in this article:

Below are the methods to find the line number:

Using next() with a Generator Expression

This method uses a generator expression with next() to efficiently find the first line containing the target word. It automatically stops searching once the word is found, making it concise and fast.

word = "writer"

with open("file1.txt", 'r') as f:
    res = next((n for n, line in enumerate(f, start=1) if word in line), None)

if res:
    print("The word", word, "is found in line number:", res)
else:
    print("The word", word, "is not found in the file.")

Output

The word writer is found in line number: 2

Explanation:

• enumerate(f, start=1): iterates lines with line numbers.
• next((n for ... if word in line), None): finds the first line number containing the word, returns None if not found.
• Conditional print: displays line number if found, else shows not found.

Using enumerate()

enumerate() lets you loop through the file lines while automatically keeping track of line numbers.

word = "writer"

with open("file1.txt", 'r') as f:
    for n, line in enumerate(f, start=1):
        if word in line:
            print("The word", word, "is found in line number:", n)
            break
    else:
        print("The word", word "is not found in the file.")

Output

The word writer is found in line number: 2

Explanation:

• enumerate(f, start=1): automatically tracks line numbers.
• if word in line: checks for the target word.

Using a Manual Counter

You can find a word’s line number by reading the file line by line and keeping a simple counter to track the current line.

word = "writer"
n = 0

with open("file1.txt", 'r') as f:
    for line in f:
        n += 1
        if word in line:
            print("The word", word, "is found in line number:", n)
            break
    else:
        print("The word", word, "is not found in the file.")

Output

The word writer is found in line number: 2

Explanation:

• n += 1: manually counts lines.
• if word in line: checks each line for the word.

Using readlines() + enumerate()

This method reads all lines into memory first. Suitable for small files, but not recommended for very large files.

word = "writer"

with open("file1.txt", 'r') as f:
    lines = f.readlines()

for i, line in enumerate(lines, start=1):
    if word in line:
        print("The word", word, "is found in line number:", i)
        break
else:
    print("The word", word, "is not found in the file.")

Output

The word writer is found in line number: 2

Explanation:

• f.readlines(): reads all lines into a list.
• enumerate(lines, start=1): iterates with line numbers starting at
• if word in line: checks each line for the word.

Related Articles:

• Find line number of a specific string or substring or word from a .txt file
• Read a file line by line