Reading and Writing Files in Python

One of the most essential features in Python is file handling. It allows you to:

Read data from files Write data to files Process external data (logs, configs, CSV, JSON, etc.) Store output for later use

Python provides a simple and intuitive way to handle files using built-in functions.

Basic Workflow

1. Open the file using open()
2. Perform read or write operation
3. Close the file (automatically using with)

Opening Files

file = open("example.txt", "r")  # Open for reading
file.close()

Reading from a File

read() — Read Entire File

with open("example.txt", "r") as file:
    content = file.read()
    print(content)

Explanation: read() reads the entire file as a string.

readline() — Read One Line at a Time

with open("example.txt", "r") as file:
    line1 = file.readline()
    line2 = file.readline()
    print(line1.strip())
    print(line2.strip())

Explanation: readline() reads one line each time it is called.

Iterating Line by Line

with open("example.txt", "r") as file:
    for line in file:
        print(line.strip())

Explanation: Looping over the file gives you each line.

Writing to a File

write() — Write Strings to File

with open("output.txt", "w") as file:
    file.write("Hello, world!\n")
    file.write("This is written to the file.\n")

Explanation: 'w' mode overwrites the file or creates it if it doesn’t exist.

Appending to a File

a Mode — Append New Content

with open("output.txt", "a") as file:
    file.write("Appending this line.\n")

Explanation: 'a' mode preserves existing content and adds new data at the end.

Closing Files

When using:

file = open("example.txt", "r")
content = file.read()
file.close()

👉 You must call file.close() yourself — otherwise, resources might stay open.

Using with Statement

with open("example.txt", "r") as file:
    content = file.read()
    print(content)

Benefits: File is automatically closed Prevents resource leaks Recommended practice!

Summary

Python supports powerful, simple file I/O:

• read(), readline(), iteration — for reading
• write(), append() — for writing Always use with open() — best practice Handling files is key for most real-world applications

Next, we will cover File Modes — understanding the different ways to open files ('r', 'w', 'a', 'b', 'x', etc.).