In the real world, data is not always stored in variables or lists. Most of the time, it lives in files—whether it’s a text file, logs, configuration data, images, or even large datasets.
That’s where File Handling in Python comes into play.
This guide will walk you through everything about opening, reading, writing, appending, closing, and managing files—and also cover advanced concepts like file modes, context managers, error handling, binary files, and JSON/CSV file handling.
What is File Handling?
File handling is simply the way we open, read, write, modify, and close files in Python.
Python provides a built-in function open() to work with files.
Opening a File
file = open("example.txt", "r")Here:
"example.txt"→ file name"r"→ mode (read mode)
File Modes in Python
| Mode | Meaning | Example |
|---|---|---|
"r" | Read (default). Error if file doesn’t exist | open("file.txt", "r") |
"w" | Write (creates new or overwrites existing) | open("file.txt", "w") |
"a" | Append (creates new if not exists, adds to end) | open("file.txt", "a") |
"x" | Exclusive creation (error if file exists) | open("file.txt", "x") |
"b" | Binary mode (images, videos, PDFs) | open("file.jpg", "rb") |
"t" | Text mode (default) | open("file.txt", "rt") |
"+" | Read + Write | open("file.txt", "r+") |
Read More: Lists in Python
Reading from a File
file = open("example.txt", "r")
content = file.read()
print(content)
file.close()Other ways:
# Read only first 10 characters
print(file.read(10))
# Read single line
print(file.readline())
# Read all lines in a list
lines = file.readlines()
print(lines)Loop through lines:
with open("example.txt", "r") as file:
for line in file:
print(line.strip())Writing to a File
file = open("example.txt", "w")
file.write("Hello, Python learners!\n")
file.write("This is file handling in action.\n")
file.close()⚠ Using "w" overwrites the file.
To append new content:
with open("example.txt", "a") as file:
file.write("This line is appended.\n")Best Practice: Using with Statement
with ensures files close automatically:
with open("example.txt", "r") as file:
data = file.read()
print(data)Reading & Writing Together
with open("notes.txt", "w+") as file:
file.write("First note.\n")
file.seek(0) # Move pointer back to start
print(file.read())Working with File Paths
- Absolute path:
with open("C:/Users/SmartTejas/Documents/data.txt", "r") as file:
print(file.read())- Relative path:
with open("data.txt", "r") as file:
print(file.read())Error Handling in File Handling
Sometimes the file may not exist. Use try-except:
try:
with open("missing.txt", "r") as file:
print(file.read())
except FileNotFoundError:
print("File not found. Please check the filename.")Working with Binary Files
with open("image.jpg", "rb") as file:
data = file.read()
print(f"File size: {len(data)} bytes")Writing binary files:
with open("copy.jpg", "wb") as file:
file.write(data)File Handling with JSON
JSON (JavaScript Object Notation) is common for storing structured data.
import json
data = {"name": "Tejas", "age": 25, "city": "Raipur"}
# Writing JSON
with open("data.json", "w") as file:
json.dump(data, file)
# Reading JSON
with open("data.json", "r") as file:
loaded = json.load(file)
print(loaded)File Handling with CSV
CSV (Comma-Separated Values) is used in spreadsheets.
import csv
# Writing CSV
with open("students.csv", "w", newline="") as file:
writer = csv.writer(file)
writer.writerow(["Name", "Age", "Course"])
writer.writerow(["Ankit", 22, "Python"])
writer.writerow(["Riya", 21, "Data Science"])
# Reading CSV
with open("students.csv", "r") as file:
reader = csv.reader(file)
for row in reader:
print(row)Useful File Methods
| Method | Use |
|---|---|
file.read(size) | Read characters |
file.readline() | Read one line |
file.readlines() | Read all lines as list |
file.write(str) | Write string |
file.writelines(list) | Write multiple lines |
file.seek(pos) | Move pointer |
file.tell() | Current pointer position |
file.close() | Close file |
Real-Life Project: Simple Contact Saver
# Contact Saver using File Handling
def add_contact():
name = input("Enter name: ")
phone = input("Enter phone: ")
# Read all contacts first
with open("contacts.txt", "r") as file:
contacts = file.read()
if phone in contacts:
print(f"This {phone} is already saved in your contact.")
else:
with open("contacts.txt", "a") as file:
file.write(f"{name} - {phone}\n")
print("Contact saved!")
def view_contacts():
with open("contacts.txt", "r") as file:
print("Your Contacts:")
for line in file:
print(line.strip())
while True:
choice = input("\n1. Add Contact\n2. View Contacts\n3. Exit\nChoose: ")
if choice == "1":
add_contact()
elif choice == "2":
view_contacts()
elif choice == "3":
break
else:
print("Invalid choice.")Final Thoughts
File handling is a core Python skill.
With it, you can:
- Save & load user data
- Store logs and configurations
- Work with CSV/JSON for data science
- Even handle binary files like images & PDFs
FAQs – File Handling in Python
What are file modes in Python?
File modes define how a file is opened. Common modes:
"r"→ read"w"→ write (overwrite)"a"→ append"b"→ binary mode"t"→ text mode (default)"+"→ read + write
Why should I use with open() instead of open()?
Using with open() is recommended because it automatically closes the file once the block is finished, preventing memory leaks.
What’s the difference between JSON and CSV in Python?
JSON → for structured hierarchical data (like dictionaries)
CSV → for tabular data (rows and columns, like Excel)
What real-life applications use file handling in Python?
Storing user contacts
Writing log files
Reading configuration settings
Processing CSV/JSON for data analysis
Saving scraped data from the web
What’s Next?
In the next post, we’ll learn about the Error Handling in Python