File Handling in Python

File handling is a crucial part of Python programming. It allows you to store, retrieve, and manipulate data stored in files such as text or binary files.

1. Opening and Closing a File

This example shows how to open and close a text file.

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

Explanation: This code opens a file named example.txt in read mode (r), prints its content, and then closes the file.

2. Writing to a File

file = open("output.txt", "w")
file.write("Hello, world!")
file.close()

Explanation: This code creates or overwrites output.txt and writes "Hello, world!" to it.

3. Appending to a File

file = open("output.txt", "a")
file.write("\nAppended line.")
file.close()

Explanation: This opens the file in append mode and adds a new line without overwriting existing content.

4. Reading Line by Line

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

Explanation: This reads each line from the file and prints it without extra newline characters.

5. Using `with` Statement (Context Manager)

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

Explanation: The with statement automatically handles file closing, even if an error occurs.

6. File Modes Explained

r – Read (default mode)
w – Write (overwrite)
a – Append
r+ – Read and write
wb – Write binary
rb – Read binary

7. Reading a File into a List

with open("example.txt") as file:
    lines = file.readlines()
    print(lines)

Explanation: The readlines() method reads all lines and returns them as a list.

8. Checking if File Exists

import os
if os.path.exists("example.txt"):
    print("File exists!")
else:
    print("File does not exist.")

Explanation: This checks whether a file exists using the os module.

9. Reading a Binary File

with open("image.png", "rb") as file:
    content = file.read()
    print("Bytes read:", len(content))

Explanation: This opens an image in binary read mode and prints the byte size.

10. Writing to a File Using a List

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

Explanation: This code writes multiple lines to a file using writelines().

File Handling in Python