Python bytes() function

In Python, for binary data manipulation, we use the bytes() function. Before getting to know the bytes() function in Python, let's get a brief idea about Bits, Bytes, and Hexadecimal numbers.

Bits and Bytes

Hexadecimal numbers

Now, let's see what is bytes() function in Python:

Whats is bytes() in Python?

1. strings
   
2. byte sequences
   
3. byte arrays
4. lists
5. tuples
6. range objects
   

Points To Remember:

• The bytes object is immuatble
  
• The range of integers in bytes object should be 0<=x<256.

Syntax of bytes()

bytes(source, encoding, error)

As seen in the syntax above, the bytes() function accepts 3 parameters:

• source(optional) - This parameter allows us to initialize the bytes object. It is used while creating the bytes object. The source can be integers, strings, iterable(list, tuple, etc).
• encoding(optional) - If the source parameter is a string, then you should pass an encoding( like UTF/ASCII) then converts the string to bytes.
• error(optional) - specifies a way to handle the error if any arises when encoding conversion fails. (used only when source parameter is a string)

​All three parameters seen in the above syntax are optional.

Return Type of bytes()

print(type(bytes()))

How does bytes() work?

Let's see some examples of the bytes() function:

Example 1: Integer as a Parameter

If the source parameter is an Integer, Python's bytes() function will create an array of a provided integer size, all initialized to NULL.

print(bytes())

a = 4
print(bytes(a))

As seen in the above example:​

1. Without an argument, an array of size 0 is returned.
   
2. If we pass only one integer argument to the bytes() function, it uses this input argument to determine how many bytes should be created. It just uses bytes with the value 0, in byte notation x00 to fill the byte.

The b prefix signifies a bytes string literal.

\x signifies Hexadecimal number.

Example 2 : Iterable as a Parameter

If the source parameter is iterable like Lists in Python, then it returns an array of the size of iterable with elements equal to iterable elements (range 0 <= x < 256).

a = [1, 5, 8]
print(bytes(a))

Example 3: String as a Parameter

s = "CodesDope"

# 'utf-8' encoding
array1 = bytes(s, 'utf-8')

# 'utf-16' encoding
array2 = bytes(s, 'utf-16')

print(array1)
print(array2)

# actual bytes in the string
for byte in array1:
    print(byte, end=' ')
print("")
for byte in array2:
    print(byte, end=' ')<br/>

• strict - Raises the default UnicodeDecodeError in case of encode failure.
  
• ignore - Ignores the unencodable character and encodes the remaining string.
  
• replace -  Replaces the unencodable character with a ‘?’.
  

string = 'CÖdesDÖpe'
print("When the error is strict : " +
      str(bytes(string, 'ascii', errors='strict')))

string = 'CÖdesDÖpe'
print("When the error is ignore : " +
      str(bytes(string, 'ascii', errors='ignore')))

3. when encoding = ASCII and error = replace:

string = 'CÖdesDÖpe'
print("When the error is replace : " +
      str(bytes(string, 'ascii', errors='replace')))

When does bytes() give a TypeError?

1. If we try to modify the bytes object, it will raise a TypeError since it is immutable by nature. Below is an example for the same:

elements = [1,2,3,4]
byte_obj = bytes(elements)
print(byte_obj)

byte_obj[0] = 5
print(byte_obj)

2. If the source parameter is None, it will raise a TypeError, as it cannot convert a None object to a byte array. Below is an example for the same:

b = bytes(None)
print(b)

When does bytes() give a ValueError?

# This will run with no error
l = [0,2,255,7]
byte_obj = bytes(l)
print(byte_obj)

# This will throw an error since 999>255
l = [999,5,40]
byte_obj = bytes(l)
print(byte_obj)

# This will throw an error since -10<0
l = [-10,4,1]
byte_obj = bytes(l)
print(byte_obj)

l = [1,2,256]
byte_obj = bytes(l)
print(byte_obj)