In Python, the open() function and the with statement are used for file handling — i.e., to read, write, or modify files.
They are an essential part of working with external files such as text files, logs, or CSV data.

🔹 open() Function

The open() function is used to open a file and returns a file object that can be used to perform operations like reading or writing.

Syntax:

open(filename, mode)

open(filename, mode)

Parameters:

Common File Modes

🧩 Example 1: Opening and Reading a File

# Open a file in read mode
file = open("sample.txt", "r")
content = file.read()
print(content)
file.close()  # Always close the file

# Open a file in read mode
file = open("sample.txt", "r")
content = file.read()
print(content)
file.close()  # Always close the file

Output (example):

Hello, this is a sample text file.

Hello, this is a sample text file.

🧩 Example 2: Writing to a File

file = open("example.txt", "w")
file.write("Hello, Dheeraj!\nWelcome to Python file handling.")
file.close()

file = open("example.txt", "w")
file.write("Hello, Dheeraj!\nWelcome to Python file handling.")
file.close()

Output:
A new file example.txt will be created with the written text.

🧩 Example 3: Appending Data to a File

file = open("example.txt", "a")
file.write("\nThis line is appended later.")
file.close()

file = open("example.txt", "a")
file.write("\nThis line is appended later.")
file.close()

Output (file content):

Hello, Dheeraj!
Welcome to Python file handling.
This line is appended later.

Hello, Dheeraj!
Welcome to Python file handling.
This line is appended later.

🔹 The with Statement (Context Manager)

The with statement simplifies file handling by automatically closing the file once the block of code is executed — even if an error occurs.
It’s considered best practice for file I/O operations.

Syntax:

with open(filename, mode) as variable:
    # perform file operations

with open(filename, mode) as variable:
    # perform file operations

🧩 Example 4: Reading a File Using with

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

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

Output:

Hello, this is a sample text file.

Hello, this is a sample text file.

Explanation:

• The file is automatically closed when the with block ends.
• You don’t need to call file.close() manually.

🧩 Example 5: Writing with with Statement

with open("notes.txt", "w") as file:
    file.write("This file was written using 'with' statement.")

with open("notes.txt", "w") as file:
    file.write("This file was written using 'with' statement.")

Output:
A new file notes.txt is created and automatically closed after writing.

🧩 Example 6: Reading File Line by Line

with open("sample.txt", "r") as file:
    for line in file:
        print(line.strip())

with open("sample.txt", "r") as file:
    for line in file:
        print(line.strip())

Output:

Hello, this is a sample text file.

Hello, this is a sample text file.

🧩 Example 7: Handling Binary Files

with open("image.jpg", "rb") as file:
    content = file.read()
    print("File size:", len(content), "bytes")

with open("image.jpg", "rb") as file:
    content = file.read()
    print("File size:", len(content), "bytes")

Output:

File size: 20480 bytes

File size: 20480 bytes

🔹 Advantages of Using with Over open()

🔹 In Summary

✅ In short:

• Use open() to work with files.
• Use with to automatically close them and write clean, safe code.