File Handling in Python – Reading, Writing, and Managing Files

File handling is an essential part of programming, allowing us to read, write, and manipulate files. Python provides built-in functions to work with different file formats, including text files, CSV, JSON, and binary files.

In this post, we’ll cover:

✅ Opening and closing files in Python
✅ Reading and writing text files
✅ Handling CSV and JSON files
✅ Best practices for file handling

Let’s get started! 🚀

1️⃣ Opening and Closing Files in Python

Python provides the open() function to work with files.

🔹 Basic Syntax:

file = open("example.txt", "r")  # Open file in read mode
content = file.read()  # Read file content
file.close()  # Close the file after use

✅ Using with Statement (Best Practice)

The with statement automatically closes the file after use, avoiding potential memory leaks.

with open("example.txt", "r") as file:
    content = file.read()  
    print(content)  # File is automatically closed after this block

🔥 Why Use with?

✅ No need to call close() manually.
✅ Prevents issues if an exception occurs.
✅ Improves readability and safety.

2️⃣ Reading Files in Python

Python provides multiple ways to read file content:

✅ 1. Reading the Entire File (read())

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

✅ 2. Reading Line by Line (readline())

with open("example.txt", "r") as file:
    first_line = file.readline()  # Reads first line
    print(first_line)

✅ 3. Reading All Lines (readlines())

with open("example.txt", "r") as file:
    lines = file.readlines()  # Returns a list of lines
    for line in lines:
        print(line.strip())  # Remove newline characters

3️⃣ Writing Files in Python

Python allows writing to files using different modes:

Mode	Description
"w"	Write mode (overwrites file if exists)
"a"	Append mode (adds to file without overwriting)
"x"	Create mode (fails if file already exists)

✅ 1. Writing to a File (write())

with open("output.txt", "w") as file:
    file.write("Hello, Python!\n")
    file.write("This is a new line.\n")

📌 Note: "w" mode overwrites the file if it exists.

✅ 2. Appending to a File (a mode)

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

4️⃣ Working with CSV Files in Python

CSV (Comma-Separated Values) files store tabular data. Python’s csv module makes it easy to read and write CSV files.

✅ 1. Reading a CSV File

import csv

with open("data.csv", "r") as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)  # Each row is a list

✅ 2. Writing to a CSV File

import csv

with open("output.csv", "w", newline="") as file:
    writer = csv.writer(file)
    writer.writerow(["Name", "Age", "City"])  # Header row
    writer.writerow(["Alice", 30, "New York"])
    writer.writerow(["Bob", 25, "London"])

5️⃣ Working with JSON Files in Python

JSON (JavaScript Object Notation) is widely used for storing structured data. Python’s json module allows easy parsing and writing of JSON files.

✅ 1. Reading a JSON File

import json

with open("data.json", "r") as file:
    data = json.load(file)  # Convert JSON to dictionary
    print(data)

✅ 2. Writing to a JSON File

import json

data = {
    "name": "Alice",
    "age": 30,
    "city": "New York"
}

with open("output.json", "w") as file:
    json.dump(data, file, indent=4)  # Write JSON with indentation

6️⃣ Handling Binary Files (Images, Audio, etc.)

Python can also work with binary files like images and audio.

✅ Reading a Binary File

with open("image.jpg", "rb") as file:  # Open in binary mode
    data = file.read()
    print("Binary data length:", len(data))

✅ Writing a Binary File

with open("copy.jpg", "wb") as file:
    file.write(data)  # Writing binary data

7️⃣ Handling Exceptions While Working with Files

Handling errors ensures smooth execution.

try:
    with open("nonexistent.txt", "r") as file:
        content = file.read()
except FileNotFoundError:
    print("Error: File not found!")
except Exception as e:
    print(f"An error occurred: {e}")

✅ Why Use Exception Handling?

Prevents crashes if the file doesn’t exist.

Helps provide meaningful error messages.

8️⃣ Best Practices for File Handling in Python

✅ Use the with statement to ensure files are closed properly.
✅ Always handle exceptions when working with files.
✅ Use absolute paths for reliability.
✅ Avoid reading large files into memory—use streaming techniques instead.
✅ Use appropriate file modes ("r", "w", "a", "rb", "wb") based on requirements.

🔹 Conclusion

✅ Text Files – Read and write using "r" and "w".
✅ CSV Files – Use the csv module for structured data.
✅ JSON Files – Convert Python dictionaries to JSON.
✅ Binary Files – Handle images and non-text files.
✅ Exception Handling – Avoid crashes by managing errors properly.

Mastering file handling is essential for working with real-world applications. 🚀

What’s Next?

In the next post, we’ll explore Python’s Concurrency Model, covering threads, multiprocessing, and async programming. Stay tuned! 🔥

💬 What Do You Think?

How do you use file handling in your projects? What’s your preferred way to manage files? Let’s discuss in the comments! 💡