How to convert hex str into int array

Question

I have strings of hex, for exemple ’01ff6fee32785e366f710df10cc542B4′ and I am trying to convert them (efficiently) into an int array 2 characters by 2 characters like [1,255,…].

I tried

c = '8db6796fee32785e366f710df10cc542B4' 
c2=[int(x,16) for x in c]

but it only takes the characters one by one.
Can i do it without using a for loop (I might be wrong but if think it would be slower) ?

Asked By: Grimsovitch

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Source

Answer 1

You could range(..) over substrings of length 2:

c = '8db6796fee32785e366f710df10cc' 
c2=[int(c[i:i+2],16) for i in range(0,len(c),2)]

So i iterates of the string with steps of 2 and you take a substring of length 2 from i to i+2 (exclusive) with c[i:i+2]. These you convert by taking int(..,16).

For your sample input it generates:

>>> c='8db6796fee32785e366f710df10cc'
>>> [int(c[i:i+2],16) for i in range(0,len(c),2)]
[141, 182, 121, 111, 238, 50, 120, 94, 54, 111, 113, 13, 241, 12, 12]

The last element is 12 because the length of your string is odd, so it takes c as the last element to parse.

Answered By: Willem Van Onsem

Answer 2

>>> c = '8db6796fee32785e366f710df10c'
>>> [int(x) for x in bytearray.fromhex(c)]
[141, 182, 121, 111, 238, 50, 120, 94, 54, 111, 113, 13, 241, 12]
>>> list(map(int, bytearray.fromhex(c)))
[141, 182, 121, 111, 238, 50, 120, 94, 54, 111, 113, 13, 241, 12]

Two relatively simple solutions, but these will error out if the string has an odd number of characters which might or might not be what you want.

Answered By: Dave Rove

Answer 3

For an alternate approach

hex_string = '8db6796fee32785e366f710df10cc542B4'
a = bytearray.fromhex(hex_string)
b = list(a)
print(b)

Answered By: Benjamin Fasken

Answer 4

I found that converting to bytearray first then to numpy array is 15x faster than using int(..) parsing:

%%time 
for p in df.phash:
    np.frombuffer(bytearray.fromhex(p), np.uint8)

Answered By: John Jiang

How to convert hex str into int array

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