How to use the 'hex' encoding in Python 3.2 or higher?

Question

In Python 2, to get a string representation of the hexadecimal digits in a string, you could do

>>> '\x12\x34\x56\x78'.encode('hex')
'12345678'

In Python 3, that doesn't work anymore (tested on Python 3.2 and 3.3):

>>> '\x12\x34\x56\x78'.encode('hex')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
LookupError: unknown encoding: hex

There is at least one answer here on SO that mentions that the hex codec has been removed in Python 3. But then, according to the docs, it was reintroduced in Python 3.2, as a "bytes-to-bytes mapping".

However, I don't know how to get these "bytes-to-bytes mappings" to work:

>>> b'\x12'.encode('hex')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'bytes' object has no attribute 'encode'

And the docs don't mention that either (at least not where I looked). I must be missing something simple, but I can't see what it is.

I would argue against closing this as a dupe. This question is specifically about Python 3.2 where the `hex` codec is officially back (but harder to find). The linked question is about Python 3.1. — Tim Pietzcker, Oct 16 '12 at 16:07

score 31 · Accepted Answer · edited Jun 02 '14 at 15:00

31

You need to go via the codecs module and the hex_codec codec (or its hex alias if available^*):

codecs.encode(b'\x12', 'hex_codec')

_{* From the documentation: "Changed in version 3.4: Restoration of the aliases for the binary transforms".}

edited Jun 02 '14 at 15:00

Cristian Ciupitu

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answered Oct 16 '12 at 14:58

ecatmur

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5

Don't you mean `codecs.encode(b'\x12', 'hex_codec')`? With `'hex'` I only get `LookupError: unknown encoding: hex` – mata Oct 16 '12 at 17:22
3

The docs say `hex` is an alias in 3.2, but my 3.2.3 installation had the same error. – Mark Tolonen Oct 16 '12 at 20:11
2

While I can't find a reference to a bugfix, it looks like `hex` is working again as of 3.4. – Eli Collins Jan 08 '14 at 17:55
Thankyou ! you save my day :) – DrNutsu Aug 23 '16 at 11:40

score 14 · Answer 2 · edited Oct 31 '13 at 23:08

14

Yet another way using binascii.hexlify():

>>> import binascii
>>> binascii.hexlify(b'\x12\x34\x56\x78')
b'12345678'

edited Oct 31 '13 at 23:08

Craig McQueen

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answered Oct 16 '12 at 16:19

Mark Tolonen

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So you took a glance at the so-called dupe, yes? :) – Tim Pietzcker Oct 16 '12 at 20:47
1

No, that's the way I usually do it :) – Mark Tolonen Oct 17 '12 at 03:06

score 10 · Answer 3 · edited Oct 31 '13 at 22:51

10

Using base64.b16encode():

>>> import base64
>>> base64.b16encode(b'\x12\x34\x56\x78')
b'12345678'

edited Oct 31 '13 at 22:51

Craig McQueen

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answered Oct 16 '12 at 15:50

dan04

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score 9 · Answer 4 · edited Sep 09 '14 at 12:49

9

binascii methods are easier by the way:

>>> import binascii
>>> x=b'test'
>>> x=binascii.hexlify(x)
>>> x
b'74657374'
>>> y=str(x,'ascii')
>>> y
'74657374'
>>> x=binascii.unhexlify(x)
>>> x
b'test'
>>> y=str(x,'ascii')
>>> y
'test'

edited Sep 09 '14 at 12:49

Cristian Ciupitu

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answered Nov 18 '12 at 07:03

iMagur

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`str(x,'ascii')` is better spelt `x.decode('ascii')` – Eric Sep 09 '14 at 12:55
3

`binascii` also seems faster, for anyone who cares. – Wojciech Kaczmarek Jul 26 '16 at 10:10

How to use the 'hex' encoding in Python 3.2 or higher?

4 Answers4

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