Python’s readline() Method: A Comprehensive Guide

In this tutorial, we will be exploring the Python method readline(). This function is a part of Python’s built-in file handling methods and is used to read a single line from the file.

Usage of readline()

The syntax for using the readline() method is as follows:

file.readline()

This method reads a line from the file and returns it in string format. If there are no more lines to read, it returns an empty string.

A Simple Walkthrough

To illustrate how readline() works, let’s consider a simple text file named ‘test.txt’ with the following content:

Line 1
Line 2
Line 3

We can use readline() to read this file line by line as shown below:

file = open('test.txt', 'r')
print(file.readline()) # Output: Line 1

print(file.readline()) # Output: Line 2

print(file.readline()) # Output: Line 3

print(file.readline()) # Output: ''
file.close()

Note that each call to readline() reads the next line in the file. When all lines have been read, further calls return an empty string.

Tips for Proper Usage

• Error Handling: Always ensure that your code handles potential errors such as trying to open a non-existent file or not having permission to access a certain file.
• Closing Files: It’s a good practice to always close the file after you’re done with it. This can be done using the close() method.
• Using With Statement: You can use the with statement which automatically takes care of closing the file once operations are completed, even if an error occurs during operation.

In conclusion, Python’s readline() method is a simple yet powerful tool for reading files line by line. It’s easy to use and highly effective when dealing with large files where reading the entire content into memory isn’t feasible.

Acknowledgements

We hope this tutorial has been helpful in understanding how to use Python’s readline() function. Happy coding!