How to open a binary file in read and write mode with Python?

A binary file is a file that consists of a series of 1's and 0's, typically used to represent data such as images, audio, video, and executables. Python provides the built-in open() function to work with binary files in read and write mode.

The open() Function

The Python open() function is a built-in function used to open files. It accepts a file path as a parameter and returns a file object. You can specify the mode parameter to control how the file is opened.

Syntax

open(file, mode)

Binary File Modes

To open a binary file in read and write mode, Python provides two main modes ?

• rb+ − Opens an existing file for both reading and writing in binary format. The file must exist or it raises FileNotFoundError. File contents are not cleared.
• wb+ − Opens a file for both reading and writing in binary format. Creates a new file if it doesn't exist. Clears existing content to zero length.

Note: Use 'rb+' to read and modify existing binary files. Use 'wb+' to start with a fresh file.

Example: Using wb+ Mode

The 'wb+' mode creates a new file or clears existing content, then allows both reading and writing ?

# Using wb+ mode to write and read
with open('example.bin', 'wb+') as file:
    # Write binary data
    file.write(b'Welcome to Tutorialspoint!!')
    
    # Move to beginning to read
    file.seek(0)
    content = file.read()
    print(content)

b'Welcome to Tutorialspoint!!'

Example: Using rb+ Mode

The 'rb+' mode opens an existing binary file for reading and writing without clearing content ?

# First create a file with some content
with open('data.bin', 'wb') as file:
    file.write(b'Hello World')

# Now use rb+ to read and modify
with open('data.bin', 'rb+') as file:
    # Read existing content
    print("Original:", file.read())
    
    # Write at the beginning
    file.seek(0)
    file.write(b'Hi')
    
    # Read the modified content
    file.seek(0)
    print("Modified:", file.read())

Original: b'Hello World'
Modified: b'Hi World'

Key Differences

Note: The 'b' prefix in the output (like b'Hello') indicates a byte string, which represents binary data rather than Unicode text.

Conclusion

Use 'wb+' mode when you need to create a fresh binary file with read/write access. Use 'rb+' mode when you want to modify an existing binary file without losing its original content.