Python File Handling

What You’ll Learn in This Blog

• What is file handling in Python?
• Opening a file (modes: read, write, append)
• Reading from files (read(), readline(), readlines())
• Writing and appending to files
• Using with statement for clean file handling
• Working with file paths
• Best practices and common mistakes

What is File Handling?

File handling allows your Python program to interact with files on your computer: reading data from files or writing data to them.

Python provides built-in functions to work with files using:

open(filename, mode)

File Modes in Python

Opening a File

file = open("data.txt", "r")  # Opens in read mode

Always close a file when you;re done:

file.close()

But instead of manually opening and closing, it's better to use with statement (explained below).

Reading from a File

Method 1: read(): Reads the entire file

with open("data.txt", "r") as f:
	content = f.read()
	print(content)

Method 2: readline(): Reads one line at a time

with open("data.txt", "r") as f:
	line1 = f.readline()
	line2 = f.readline()
	print(line1, line2)

Method 3: readlines(): Reads all lines into a list

with open("data.txt", "r") as f:
	lines = f.readlines()
	for line in lines:
		print(line.strip())

Writing to a File

'w' mode overwrites the file:

with open("data.txt", "w") as f:
	f.write("Hello, Akash!\n")
	f.write("Welcome to Python file handling tutorial.")

Appending to a File

'a' mode adds content to the end:

with open("data.txt", "a") as f:
	f.write("\nThis is an additional line.")

Using with Statement (Context Manager)

The with statement automatically close the file even if an error occurs.

with open("data.txt", "r") as f:
	data = f.read()
	print(data)
# File is now close automatically

Why use with?

• Avoids forgetting file.close()
• Cleaner and safer code

Handling File Paths

To avoid errors across platforms, use os.path:

import os

path = os.path.join("folder", "data.txt")
with open(path, "r") as f:
	print(f.read())

or use absolute paths carefully:

with open("/home/akash/documents/data.txt") as f:
	...

Common Mistakes to Avoid

• Not closing the file manually (if not using with)
• Using 'w' instead of 'a' when you want to append
• Reading a file that doesn't exist (check with os.path.exists() if needed)

Practice Task

🔸 Create  text file named log.txt. Write a Python script that:

1. Appends the current timestamp and a message to the file each tiime it's run.
2. Then reads and prints the entire content of log.txt.

💡 Hint: Use datetime.now() from the datetime module.

Summary