Python bytes() Function

The bytes() function in Python is used to create an immutable sequence of bytes. It is commonly used when working with binary data, such as reading from or writing to files, networking, or handling encoded data.

Syntax

bytes([source[, encoding[, errors]]])

Parameters:

• source (optional) – Data to convert into bytes (e.g., string, iterable, or integer).
• encoding (optional) – Encoding to use when the source is a string.
• errors (optional) – Specifies how to handle encoding errors (e.g., 'strict', 'ignore').

Returns:

• A bytes object, which is an immutable sequence of integers in the range 0 <= x < 256.

Example 1: Creating Empty Bytes

empty = bytes()
print(empty)

b''

Example 2: Convert String to Bytes

text = "hello"
b = bytes(text, encoding="utf-8")
print(b)

b'hello'

Example 3: Create Bytes from List of Integers

data = [65, 66, 67]
b = bytes(data)
print(b)

b'ABC'

Example 4: Using Integer as Argument

b = bytes(4)
print(b)

b'\x00\x00\x00\x00'

This creates a bytes object of size 4 with each byte set to 0.

Use Cases

• Working with binary files
• Storing or transmitting encoded data
• Handling network protocols or buffered data
• Required when interacting with low-level APIs

Common Mistakes

• Forgetting to specify encoding when converting a string
• Providing numbers outside the range 0-255 in a list/iterable
• Expecting the result to be mutable (use bytearray() for mutable sequences)

Interview Tip

The bytes() function is often useful in interviews involving file I/O, sockets, or data serialization. Remember that it's immutable!

Summary

• bytes() creates immutable sequences of bytes
• Can be created from strings (with encoding), integers, or iterables
• Immutable – to change values, use bytearray()

Practice Problem

Ask the user to input a string, convert it to bytes, and print the result.

user_input = input("Enter a message: ")
b = bytes(user_input, encoding="utf-8")
print("Byte version:", b)