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
– Tim Pietzcker, Commented Oct 16, 2012 at 16:07

Cristian Ciupitu · Accepted Answer · 2014-06-02 15:00:54Z

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 2, 2014 at 15:00

Cristian Ciupitu

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answered Oct 16, 2012 at 14:58

ecatmur

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3 Comments

mata Over a year ago

Don't you mean codecs.encode(b'\x12', 'hex_codec')? With 'hex' I only get LookupError: unknown encoding: hex

Mark Tolonen Over a year ago

The docs say hex is an alias in 3.2, but my 3.2.3 installation had the same error.

Eli Collins Over a year ago

While I can't find a reference to a bugfix, it looks like hex is working again as of 3.4.

Craig McQueen · Accepted Answer · 2013-10-31 23:08:49Z

14

Yet another way using binascii.hexlify():

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

edited Oct 31, 2013 at 23:08

Craig McQueen

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answered Oct 16, 2012 at 16:19

Mark Tolonen

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2 Comments

Tim Pietzcker Over a year ago

So you took a glance at the so-called dupe, yes? :)

Mark Tolonen Over a year ago

No, that's the way I usually do it :)

Craig McQueen · Accepted Answer · 2013-10-31 22:51:05Z

11

Using base64.b16encode():

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

edited Oct 31, 2013 at 22:51

Craig McQueen

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answered Oct 16, 2012 at 15:50

dan04

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Comments

Cristian Ciupitu · Accepted Answer · 2014-09-09 12:49:27Z

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 9, 2014 at 12:49

Cristian Ciupitu

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answered Nov 18, 2012 at 7:03

iMagur

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2 Comments

Eric Over a year ago

str(x,'ascii') is better spelt x.decode('ascii')

Wojciech Kaczmarek Over a year ago

binascii also seems faster, for anyone who cares.

fabio · Accepted Answer · 2023-09-26 08:46:18Z

3

From python 3.5 you can simply use .hex():

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

answered Sep 26, 2023 at 8:46

fabio

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