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.to_bytes() in Python

Last Updated : 23 Jul, 2025
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In Python, the .to_bytes() method is used to convert an integer into its byte representation. This is useful when weneed to store or transmit data in binary format.

Example: Convert the integer 10 into bytes

Python 
num = 10
byte_data = num.to_bytes(2, 'big')
print(byte_data)

Output
b'\x00\n'

Explanation:

  • 10: The integer being converted.
  • .to_bytes(2, 'big'): 2: Specifies the byte length (2 bytes). 'big': Most significant byte first (big-endian).
  • b'\x00\n': The byte representation of 10 using big-endian format.

Syntax

int.to_bytes(length, byteorder, *, signed=False)

Parameters

  • length: The number of bytes the integer should occupy.
  • byteorder: The byte order used to represent the integer. It can be: 'big': Most significant byte first (big-endian). 'little': Least significant byte first (little-endian).
  • signed: (Optional) If True, allows the representation of negative numbers. Default is False (unsigned).

Return Type

Returns a bytes object representing the integer in the specified format.

Examples of .to_bytes() method

1. Using Little-Endian

Python 
num = 10
byte_rep = num.to_bytes(2, 'little')
print(byte_rep)

Output
b'\n\x00'

Explanation:

  • 10 in binary is 00001010, and in little-endian, it is represented as b'\n\x00'.
  • The b'\n\x00' output shows that 10 is stored as \n (10 in hexadecimal) followed by \x00 (a zero byte).

2. Representing Negative Numbers

Python 
num = -10
byte_rep = num.to_bytes(2, 'big', signed=True)
print(byte_rep)

Output
b'\xff\xf6'

Explanation:

  • -10 in two's complement (signed) using big-endian is represented as b'\xff\xf6'.
  • The b'\xff\xf6' output indicates that -10 is stored using two bytes where the first byte is 0xFF (representing the negative sign) and the second byte is 0xF6 (which is -10 in two's complement form).

3. Converting bytes back to integer

Python 
byte_data = b'\x00\x0a'
num = int.from_bytes(byte_data, 'big')
print(num)

Output
10

Explanation:

  • b'\x00\x0a' represents the byte sequence where the first byte is 0x00 (0 in decimal) and the second byte is 0x0a (10 in decimal).
  • Using big-endian byte order, this byte sequence is converted to the integer 10.

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