## 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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