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Python Bytes And ByteArray Data Types

The focus of this tutorial is on:

  • bytes
  • bytearray

Although these are not everyday data types for beginner-level applications, they become essential when dealing with low-level data such as images, audio, video, and network streams.

1. Why Do We Need Bytes?​

In many programming languages, if you want to represent a collection of numbers, you typically use arrays or lists. Similarly, in Python, we use lists for general-purpose collections.

However, there are situations where:

  • You want to store raw binary data
  • You need values strictly in the range of 0 to 255
  • You want efficient storage of byte-level information

In such cases, Python provides the bytes data type.

2. Creating a Bytes Object​

The bytes object is created using the built-in bytes() function.

l = [10, 20, 30, 40]
b = bytes(l)

print(type(b)) # <class 'bytes'>

3. Iterating Over Bytes​

Even though bytes represents binary data, you can still iterate over it like a sequence.

for x in b:
    print(x)
Output
10
20
30
40

This shows that each element inside the bytes object is treated as an integer.

4. Important Rule: Value Range (0 to 255)​

One of the most critical rules of the bytes data type is: Each value must be in the range 0 to 255.

l = [10, 20, 30, 255]
b = bytes(l)
Invalid Example
l = [10, 20, 30, 256]
b = bytes(l) # ValueError: bytes must be in range(0, 256)

5. Bytes Are Immutable​

One of the defining characteristics of the bytes type is that it is immutable, meaning:

Once a bytes object is created, its content cannot be modified.

l = [10, 20, 30, 40]
b = bytes(l)

print(b[0])   # Output: 10

Now, try modifying:

b[0] = 77 # TypeError: 'bytes' object does not support item assignment

6. Introducing Bytearray​

At this point, you might naturally ask:

"What if I want a mutable version of bytes?" This is exactly where bytearray comes into the picture.

7. Creating a Bytearray​

Just like bytes, we use a built-in function:

l = [10, 20, 30, 40]
b = bytearray(l)

print(type(b)) # <class 'bytearray'>

8. Accessing Elements​

print(b[0])     # 10
print(b[-1])    # 40

9. Value Range Rule Still Applies​

Even for bytearray, values must be between 0 and 255.

l = [10, 20, 30, 256]
b = bytearray(l) # ValueError: byte must be in range(0, 256)

10. Bytearray Is Mutable​

This is the key difference.

l = [10, 20, 30, 40]
b = bytearray(l)

b[0] = 77

for x in b:
    print(x)
Output
77
20
30
40

Here, the value 10 has been successfully replaced with 77.