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split a 256 bit hash into 32 bit prefix in python

Answer 1

+3 A:

32 bits is the first 4 bytes. So you can slice the byte array.

hash_obj.digest()[:4]

You can take that and use it as a dictionary key.

EDIT

I'm not sure if you need the hex representation, that would be.

hash_obj.hexdigest()[:8]

mikerobi 2010-10-26 00:00:02

working like a charm, thank you. is the slice indiciating the number of bits or bytes? how can I tell the difference? IE why is hex :8?

Stev0 2010-10-27 03:17:44

@Stev0, with ASCII text, it takes 1 byte (8 bits) to store a character, so taking the first 4 characters gives you 32 bits (4*8). I use the term character loosely, depending on the python version it might actually be a byte array. In hexidecimal notation, each character represents 4 bits, so to represent a byte you need 2 characters, thus you need the first 8 characters. Just to be clear, the hex version is a human friendly representation of the first 32 bits, the non hex form is the first 32 bits. http://en.wikipedia.org/wiki/Hexadecimal

mikerobi 2010-10-27 03:30:48

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split a 256 bit hash into 32 bit prefix in python

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