Python .unhexlify()

The binascii.unhexlify() method takes a string (or bytes) of hexadecimal digits and returns the corresponding binary data (as a bytes object). It is the inverse of binascii.hexlify(). The input must contain an even number of hex digits (upper or lower case), else it raises a binascii.Error.

Syntax

binascii.unhexlify(hexstr)

Parameters:

• hexstr: A string (or bytes) that represents hexadecimal digits. Must contain an even number of hex digits.

Return value:

Returns a bytes object that represents the binary data produced by decoding the hex string. Raises binascii.Error if hexstr has odd length or contains non-hex characters.

Example 1

In this example, a hex string representing ASCII characters is converted into readable bytes, then decoded to a text string:

import binascii

hex_string = "48656c6c6f20576f726c64"  # “Hello World” in hex
binary_data = binascii.unhexlify(hex_string)
text = binary_data.decode('utf-8')
print(text)

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The output of this code is:

Hello World

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Example 2

In this example, a hex string representing a small binary file header is converted into bytes and then its first few bytes are printed in integer form:

import binascii

hex_string = "424D368403000000"  # Typical “BM” header for a bitmap file
binary_data = binascii.unhexlify(hex_string)
print(binary_data)
print(list(binary_data[:4]))

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The output of this code is:

b'BM6\x84\x03\x00\x00\x00'
[66, 77, 54, 132]

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Codebyte Example

In this example, a hex-encoded network message is converted into bytes for processing (e.g., checksum or parsing):

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Frequently Asked Questions

1. What is binascii.unhexlify() in Python?

binascii.unhexlify() is a method that decodes a string of hexadecimal digits into the equivalent binary data (a bytes object).

2. What does the binascii module do in Python?

The binascii module provides low-level functions for converting between binary data and ASCII-encoded binary representations (e.g., hex, base64).

3. What is binascii.Error in Python base64?

Some binascii functions (such as those used by base64 wrappers) raise binascii.Error when the input doesn’t conform to the expected format (e.g., invalid characters or incorrect padding).