python 2.7 equivalent of built-in method int.from_bytes

Question

I'm trying to make my project python2.7 and 3 compatible and python 3 has the built in method int.from_bytes. Does the equivalent exist in python 2.7 or rather what would be the best way to make this code 2.7 and 3 compatible?

>>> int.from_bytes(b"f483", byteorder="big")
1714698291

If you're specifically looking for a cross-version solution then you should make this clear in the title. — Ignacio Vazquez-Abrams, May 22 '15 at 17:45

dawg · Accepted Answer · 2015-05-22T18:24:43.853

27

You can treat it as an encoding (Python 2 specific):

>>> int('f483'.encode('hex'), 16)
1714698291

Or in Python 2 and Python 3:

>>> int(codecs.encode(b'f483', 'hex'), 16)
1714698291

The advantage is the string is not limited to a specific size assumption. The disadvantage is it is unsigned.

edited May 22 '15 at 18:24

answered May 22 '15 at 18:09

dawg

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hah I like this solution ... alot ... its one I would not have thought of :) it has the added advantage of not having to know anything about the input – Joran Beasley May 22 '15 at 18:10
Yours is better really cause it should work in Python 2 and 3. Thanks tho – dawg May 22 '15 at 18:11
What would be the reverse of this? I'd like to retrieve the original byte string from the integer – vonec May 09 '18 at 01:07
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What about `ord(b'\x11')`? – deed02392 Mar 04 '19 at 10:58

Joran Beasley · Answer 2 · 2015-05-22T18:09:50.480

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struct.unpack(">i","f483")[0]

maybe?

> means big-endian and i means signed 32 bit int

see also: https://docs.python.org/2/library/struct.html

edited May 22 '15 at 18:09

answered May 22 '15 at 17:39

Joran Beasley

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it won't work for anything bigger than int32 of course. any hints? – Janus Troelsen Jul 26 '17 at 20:42
When the bytes is less than 4 this won't work, when it would have worked for int.from_bytes() – Tatarize Dec 31 '18 at 08:10

SanketDG · Answer 3 · 2015-05-22T19:29:44.613

7

Use the struct module to unpack your bytes into integers.

import struct
>>> struct.unpack("<L", "y\xcc\xa6\xbb")[0]
3148270713L

edited May 22 '15 at 19:29

answered May 22 '15 at 17:55

SanketDG

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that just unpacks them into bytes ... he wants them all as 1 32 bit integer ... maybe bigger ... but you are right that stuct is the module to use :) – Joran Beasley May 22 '15 at 18:11
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I didn't realize he needed the actual integer values, but yeah, fixed. – SanketDG May 22 '15 at 19:31

score 1 · Answer 4 · answered Apr 04 '19 at 10:06

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> import binascii

> barray = bytearray([0xAB, 0xCD, 0xEF])
> n = int(binascii.hexlify(barray), 16)
> print("0x%02X" % n)

0xABCDEF

answered Apr 04 '19 at 10:06

Dan

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python 2.7 equivalent of built-in method int.from_bytes

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