Unhexlify

Unhexlify is a function in Python’s standard library module binascii that converts a hex-encoded string back into binary data. It is the inverse operation of hexlify, which converts binary data to a hexadecimal string.

The function signature is binascii.unhexlify(hexstr). The input must contain an even number of hexadecimal digits (0-9, a-f, A-F). It can be provided as a str or as a bytes-like object containing ASCII hex digits. In Python 3, unhexlify returns a bytes object (in Python 2 it returns a str of bytes). If the input contains non-hex characters or has an odd length, binascii.Error is raised.

Example:

import binascii

data = binascii.unhexlify('48656c6c6f') # yields b'Hello'

data2 = binascii.unhexlify(b'48656c6c6f') # also yields b'Hello' in Python 3

Unhexlify is commonly used to decode data that has been represented in hexadecimal form, such as cryptographic digests, binary protocols, or file formats that store binary content as hex strings. It is frequently paired with hexlify, the counterpart that converts binary data to hex.