Python Hex String to Integer Array or List

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Problem Formulation

Given a hex string, i.e., a string of hexadecimal digits like so:

01ffa87135affcd45deebe

You want to convert a batch of k hex digits to an integer. For example with k=2, you obtain the following batches of two hex digits each:

01 ff a8 71 35 af fc d4 5d ee be

Now, convert each of those pairs of hex digits to an integer:

[1, 255, 168, 113, 53, 175, 252, 212, 93, 238, 190]

Note that if you’re looking to convert such a hex string to NumPy array, check out this tutorial instead.

One-Liner Solution

The following one-liner iterates over each k-th position of the hex string and bundles together k subsequent hex digits. It converts each of those hex digits to an integer using int(..., base=16) in a list comprehension statement.

[int(hex_str[i:i+k], base=16) for i in range(0, len(hex_str), k)]

Here’s the minimal code example:

def hex_to_int_list(hex_str, k):
    ''' Aggregates bundles of k subsequent
        hex digits to one integer. Yields a list of ints.'''
    return [int(hex_str[i:i+k], base=16) for i in range(0, len(hex_str), k)]

print(hex_to_int_list('01ffa87135affcd45deebe', 2))
# [1, 255, 168, 113, 53, 175, 252, 212, 93, 238, 190]

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If not, keep reading for the not-so-concise multi-liner solution. 🙂

Multi-Liner Solution

You can use a for loop to iterate over the k-th indices using the range() function like before.

def hex_to_int_list(hex_str, k):
    ''' Aggregates bundles of k subsequent
        hex digits to one integer. Yields a list of ints.'''
    lst = []
    for i in range(0, len(hex_str), k):
        x = hex_str[i:i+k]
        x_int = int(x, base=16)
        lst.append(x_int)
    return lst


print(hex_to_int_list('01ffa87135affcd45deebe', 2))
# [1, 255, 168, 113, 53, 175, 252, 212, 93, 238, 190]

You use slicing hex_str[i:i+k] to batch k digits at a time to a substring and convert it to an integer.

You use the list append() method to add one integer at a time to the list of ints.

You return a list of integers. If you want to return an array of integers, simply convert the list to a NumPy array using the np.array(lst) function call:

import numpy as np


def hex_to_int_list(hex_str, k):
    ''' Aggregates bundles of k subsequent
        hex digits to one integer. Yields a list of ints.'''
    lst = []
    for i in range(0, len(hex_str), k):
        x = hex_str[i:i+k]
        x_int = int(x, base=16)
        lst.append(x_int)
    return np.array(lst)


print(hex_to_int_list('01ffa87135affcd45deebe', 2))
# [  1 255 168 113  53 175 252 212  93 238 190]

Let’s use two different values for k, i.e., k=1 and k=4:

print(hex_to_int_list('01ffa87135affcd45deebe', 1))
# [ 0  1 15 15 10  8  7  1  3  5 10 15 15 12 13  4  5 13 14 14 11 14]

print(hex_to_int_list('01ffa87135affcd45deebe', 4))
# [  511 43121 13743 64724 24046   190]

Works too! 🙂

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