How to Convert a Byte String to an Integer in Python?

Converting a Byte String to an Integer in Python

In Python, you can encounter scenarios where you need to convert a string of bytes into an integer. Here's a breakdown of how to approach this conversion:

Method 1: Using from_bytes

For Python versions 3.2 and later, the int.from_bytes method provides a straightforward mechanism for performing this conversion:

<code class="python">int_from_bytes = int.from_bytes(byte_string, byteorder='big')

# or for little-endian byte order:
int_from_bytes = int.from_bytes(byte_string, byteorder='little')</code>

The 'byteorder' parameter specifies the endianness of your byte string ('big' or 'little').

Method 2: Bit Manipulation

If you prefer a bit-manipulation approach that doesn't require importing modules, you can use the following code:

<code class="python">int_from_bytes = sum(
    (ord(byte) << (i * 8)) for i, byte in enumerate(byte_string[::-1])
)</code>

This method iterates through the bytes in reverse order, multiplying each byte value by a power of 2 to create a cumulative integer.

Comparison of Methods

While both methods are efficient, the 'from_bytes' method is recommended for its simplicity and versatility. However, if you're concerned about importing dependencies, the bit-manipulation approach provides a more compact alternative.

Note on Importing Modules

Importing modules can affect performance, especially if the import process is repeated multiple times. To minimize this effect, import the required modules only once outside of the innermost loop.

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