File Handling in Python: Read, Write, and Manage Files with Ease

Python simplifies file operations like reading, writing, and appending data. This guide covers everything you need to know to work with files efficiently using Python's built-in functions.

Opening and Closing Files

1. Opening a File

Use the open() function to open a file. Specify the mode (read, write, append, etc.):

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

Common Modes:

• r: Read (default)
• w: Write (creates a new file or overwrites existing)
• a: Append (adds to an existing file)
• b: Binary mode (e.g., rb for reading binary files)

2. Closing a File

Always close files after use to free up resources:

file.close()

3. Using with Statements

Automatically close files using with:

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

Reading Files

1. Read Entire File

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

2. Read Line by Line

with open("example.txt", "r") as file:
    for line in file:
        print(line.strip())  # Strip removes newline characters

3. Read Lines into a List

with open("example.txt", "r") as file:
    lines = file.readlines()
print(lines)  # Output: ["Line 1\n", "Line 2\n", ...]

Writing to Files

1. Write to a New File

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

2. Append to an Existing File

with open("existing_file.txt", "a") as file:
    file.write("\nAppended text!")

3. Write Multiple Lines

lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
with open("multi_line.txt", "w") as file:
    file.writelines(lines)

Common File Operations

1. Check if a File Exists

Use the os module to verify file existence:

import os
if os.path.exists("example.txt"):
    print("File exists!")

2. Delete a File

import os
os.remove("file_to_delete.txt")

3. Handle Exceptions

Use try-except blocks to manage errors:

try:
    with open("missing_file.txt", "r") as file:
        print(file.read())
except FileNotFoundError:
    print("File not found!")

Working with CSV Files

1. Read CSV Files

Use the csv module for structured data:

import csv
with open("data.csv", "r") as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

2. Write CSV Files

import csv
data = [["Name", "Age"], ["Alice", 25], ["Bob", 30]]
with open("output.csv", "w") as file:
    writer = csv.writer(file)
    writer.writerows(data)

Best Practices

1. Always Use with Statements
   Ensures files are closed automatically, even if errors occur.

2. Handle Exceptions
   Prevent crashes due to missing files or permission issues.

3. Avoid Hardcoding Paths
   Use relative paths or configuration files for flexibility.

Next Steps

• Practice reading and writing text, CSV, and JSON files.
• Explore the os and shutil modules for advanced file management.
• Build projects like a log file analyzer or a data backup script.

Python’s file handling capabilities make it easy to work with data stored in files. Happy coding!