Let’s quick see about reading a particular line from a text file using Python. Whether you’re working with log files, data sets, or any other text-based resources, being able to extract specific lines programmatically is a valuable skill.

I will provide you with a Python function that efficiently reads the desired line from a file and explain how you can use it effectively in your projects.

Method 1 – Using readlines() function

Below is the simple method using readlines() function.

def read_specific_line(file_path, line_number):
    with open(file_path, 'r') as file:
        lines = file.readlines()
        if 0 < line_number <= len(lines):
            return lines[line_number - 1]
        else:
            return "Line number out of range"

The following shows example usage demonstrates how to call this function with a file path and a line number to read a specific line from the file:

file_path = 'example.txt'  # Replace 'example.txt' with your file path
line_number = 5  # Replace 5 with the line number you want to read
line = read_specific_line(file_path, line_number)
print("Line {}: {}".format(line_number, line.strip()))

In this example,

• read_specific_line function takes two arguments: file_path (the path to the file) and line_number (the line number you want to read).
• It opens the file specified by file_path in read mode.
• It reads all lines into a list using readlines() method.
• It checks if the specified line_number is within the range of lines in the file.
• If the line number is valid, it returns the line at that position (zero-based index is converted to one-based).
• If the line number is out of range, it returns a message indicating that.

Method 2 – Using if condition and looping

Let’s another method which loops through the file and locates the specific line.

def read_specific_line_alternative(file_path, line_number):
    try:
        with open(file_path, 'r') as file:
            for current_line_number, line in enumerate(file, start=1):
                if current_line_number == line_number:
                    return line.strip()
            return f"Line {line_number} not found"
    except Exception as e:
        return f"Error reading line: {e}"

Let’s see how to use the above written function:

# usage of the read_specific_line_alternative function
file_path = "example.txt"
line_number = 5

line_content = read_specific_line_alternative(file_path, line_number)
print(f"Line {line_number}: {line_content}")

Let me explain the above code in detail,

• We open the file using the open() function in read mode (‘r’) within a with statement to ensure that the file is properly closed after reading.
• We use a for loop to iterate through each line in the file. The enumerate() function is used to get both the line content and the line number simultaneously, starting from 1.
• Inside the loop, we check if the current line number matches the desired line number. If they match, we return the content of that line after stripping any leading or trailing whitespace.
• If the loop completes without finding the desired line number, we return a message indicating that the line was not found.
• Any errors that occur during the process are caught and an appropriate error message is returned.

This method provides an alternative approach that can be useful, especially for larger files where using linecache may not be the most efficient solution.

Reading specific lines from line is one of the most common operation required when you work on any projects that involve file operation to store large amount of data.