5 Best Ways to Convert ASCII Hex to Integer in Python

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💡 Problem Formulation: When working with data in Python, you may encounter hexadecimal strings that represent ASCII characters. The challenge is to convert these hexadecimal strings back into their integer representation. For instance, you might have the hex string '4A', which represents the ASCII character ‘J’, and you would want to convert it to its integer value, which is 74.

Method 1: Using int() with Base Parameter

The int() function in Python can be used to convert a hexadecimal string to an integer by specifying the base of the number system as 16.

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Here’s an example:

hex_string = '4A'
integer_value = int(hex_string, 16)
print(integer_value)

Output: 74

The above snippet demonstrates the direct usage of the in-built int() function, with the second argument specifying the base (16 for hexadecimal). This makes the conversion straightforward and readable.

Method 2: Utilizing the Built-in bytes.fromhex() Method

The bytes.fromhex() method converts a hexadecimal string to a bytes object, and then we can further convert the bytes to an integer.

Here’s an example:

hex_string = '4A'
bytes_object = bytes.fromhex(hex_string)
integer_value = int.from_bytes(bytes_object, 'big')
print(integer_value)

Output: 74

This method is useful when dealing with hex strings that represent larger numbers and need to be converted to their corresponding byte representation before becoming an integer.

Method 3: Using binascii.unhexlify() Function

For a more utility-based approach, the binascii.unhexlify() function converts a hex string to its binary representation, which can be easily turned into an integer.

Here’s an example:

import binascii

hex_string = '4A'
binary_data = binascii.unhexlify(hex_string)
integer_value = int.from_bytes(binary_data, 'big')
print(integer_value)

Output: 74

This code snippet is particularly handy when dealing with binary data processing and requires conversion between different data representations.

Method 4: Applying bytearray.fromhex()

The bytearray.fromhex() method similar to bytes.fromhex() but returns a mutable bytearray. Then, the bytearray is converted to an integer.

Here’s an example:

hex_string = '4A'
byte_array = bytearray.fromhex(hex_string)
integer_value = int.from_bytes(byte_array, 'big')
print(integer_value)

Output: 74

This method is favorable when you need an intermediate mutable form of the data before arriving at the final integer value.

Bonus One-Liner Method 5: Using List Comprehension and ord()

Python’s list comprehension combined with the ord() function can be employed for a compact hex to integer conversion.

Here’s an example:

hex_string = '4A'
integer_value = sum(ord(c) << (4 * i) for i, c in enumerate(hex_string[::-1]))
print(integer_value)

Output: 74

This one-liner uses the ord() function to get the integer value for each character in the string, shifts it by its position in the string, and sums up the resulting values. It is a more pythonic and succinct way of conversion.

Summary/Discussion

  • Method 1: int() with Base Parameter. Simple and direct. Best for small and straightforward conversions.
  • Method 2: bytes.fromhex() Method. Converts to a bytes format for extensive numerical operations. Slightly more verbose.
  • Method 3: binascii.unhexlify() Function. Useful for binary data manipulation. Requires importing an additional module.
  • Method 4: bytearray.fromhex(). Offers mutability for intermediate operations. Not necessary for direct conversions.
  • Bonus Method 5: One-Liner with List Comprehension and ord(). Compact and pythonic. May be confusing for beginners.