Python 3.1.1 string to hex

Question

I am trying to use str.encode() but I get

>>> "hello".encode(hex)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: must be string, not builtin_function_or_method

I have tried a bunch of variations and they seem to all work in Python 2.5.2, so what do I need to do to get them to work in Python 3.1?

score 100 · Accepted Answer · edited Feb 26 '10 at 11:17

100

The hex codec has been chucked in 3.x. Use binascii instead:

>>> binascii.hexlify(b'hello')
b'68656c6c6f'

edited Feb 26 '10 at 11:17

S.Lott

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answered Feb 26 '10 at 08:36

Ignacio Vazquez-Abrams

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BTW, binary codes made a comeback in version 3.2, [see docs](https://docs.python.org/3/library/codecs.html#binary-transforms) – tutuDajuju Dec 31 '15 at 13:02
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What if my string is stored in a variable? – nabil london May 30 '18 at 23:35
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That gives an error, because the argument has to be a bytes-like object. – nabil london May 31 '18 at 02:17
To convert a String to binary sequence you can use ".encode()". Example: "This is your String".encode() – PixelRayn Feb 06 '21 at 08:17
Why is this better than e.g. `b'hello'.hex()`? – Niels Abildgaard Feb 14 '22 at 11:01

pylang · Answer 2 · 2019-12-12T23:51:46.683

41

In Python 3.5+, encode the string to bytes and use the hex() method, returning a string.

s = "hello".encode("utf-8").hex()
s
# '68656c6c6f'

Optionally convert the string back to bytes:

b = bytes(s, "utf-8")
b
# b'68656c6c6f'

edited Dec 12 '19 at 23:51

answered Jun 13 '17 at 00:26

pylang

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This the way to do it for a Python 3 string variable. Lot of the answers here are regarding constants. A practical code is rarely that. – Jari Turkia Jan 30 '18 at 12:30
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Emphasis on >=Python 3.5 if you want to use `hex()` – ner0 Dec 12 '19 at 17:24

Mark Byers · Answer 3 · 2010-04-12T09:51:00.390

You've already got some good answers, but I thought you might be interested in a bit of the background too.

Firstly you're missing the quotes. It should be:

"hello".encode("hex")

Secondly this codec hasn't been ported to Python 3.1. See here. It seems that they haven't yet decided whether or not these codecs should be included in Python 3 or implemented in a different way.

If you look at the diff file attached to that bug you can see the proposed method of implementing it:

import binascii
output = binascii.b2a_hex(input)

score 23 · Answer 4 · answered Nov 24 '12 at 22:05

23

binascii methodes 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'

Hope it helps. :)

answered Nov 24 '12 at 22:05

iMagur

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binascii is also faster than the other methods. Just tested with timeit. – Simon Steinberger Dec 02 '15 at 23:12
How do you do string to hex conversion, if the string is a regular Python 3 string, not binary or a constant? – Jari Turkia Jan 30 '18 at 12:27

simhumileco · Answer 5 · 2019-12-13T08:30:35.373

21

The easiest way to do it in Python 3.5 and higher is:

>>> 'halo'.encode().hex()
'68616c6f'

If you manually enter a string into a Python Interpreter using the utf-8 characters, you can do it even faster by typing b before the string:

>>> b'halo'.hex()
'68616c6f'

Equivalent in Python 2.x:

>>> 'halo'.encode('hex')
'68616c6f'

edited Dec 13 '19 at 08:30

answered Feb 18 '19 at 12:54

simhumileco

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Thank you @ner0 for your important comment! – simhumileco Dec 13 '19 at 08:31
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No worries. If v3.4 or below is a requirement, this will do: `from binascii import hexlify str(hexlify(bytes('halo', encoding = 'utf-8')), 'ascii')` – ner0 Dec 13 '19 at 16:15
Is this because `.hex()` wasn't added until Python 3.5? A link to the changelog would have been really good in this answer as context :-) – Niels Abildgaard Feb 14 '22 at 11:03

Devy · Answer 6 · 2015-09-01T23:41:09.330

In Python 3, all strings are unicode. Usually, if you encode an unicode object to a string, you use .encode('TEXT_ENCODING'), since hex is not a text encoding, you should use codecs.encode() to handle arbitrary codecs. For example:

>>>> "hello".encode('hex')
LookupError: 'hex' is not a text encoding; use codecs.encode() to handle arbitrary codecs
>>>> import codecs
>>>> codecs.encode(b"hello", 'hex')
b'68656c6c6f'

Again, since "hello" is unicode, you need to indicate it as a byte string before encoding to hexadecimal. This may be more inline with what your original approach of using the encode method.

The differences between binascii.hexlify and codecs.encode are as follow:

binascii.hexlify

Hexadecimal representation of binary data.

The return value is a bytes object.

Type: builtin_function_or_method
codecs.encode

encode(obj, [encoding[,errors]]) -> object

Encodes obj using the codec registered for encoding. encoding defaults to the default encoding. errors may be given to set a different error handling scheme. Default is 'strict' meaning that encoding errors raise a ValueError. Other possible values are 'ignore', 'replace' and 'xmlcharrefreplace' as well as any other name registered with codecs.register_error that can handle ValueErrors.

Type: builtin_function_or_method

score 8 · Answer 7 · edited May 23 '17 at 10:31

8

base64.b16encode and base64.b16decode convert bytes to and from hex and work across all Python versions. The codecs approach also works, but is less straightforward in Python 3.

edited May 23 '17 at 10:31

Community

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answered Dec 19 '13 at 22:00

Gabriel

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This is exactly what I needed! A cross-python version way of hex encoding & decoding. Thanks ^_^ `>>> import base64 >>> key = base64.b16encode(b'0123456789abcdef') >>> base64.b16decode(key) '0123456789abcdef'` – TrinitronX Apr 17 '14 at 06:03

score 3 · Answer 8 · answered Feb 26 '10 at 08:36

3

Use hexlify - http://epydoc.sourceforge.net/stdlib/binascii-module.html

answered Feb 26 '10 at 08:36

Ofir

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It was shorter than "hexlificationize" :^) – Mark Tolonen Feb 26 '10 at 17:58

score 2 · Answer 9 · answered Feb 12 '18 at 03:33

Yet another method:

s = 'hello'

h = ''.join([hex(ord(i)) for i in s]);

# outputs: '0x680x650x6c0x6c0x6f'

This basically splits the string into chars, does the conversion through hex(ord(char)), and joins the chars back together. In case you want the result without the prefix 0x then do:

h = ''.join([str(hex(ord(i)))[2:4] for i in s]);

# outputs: '68656c6c6f'

Tested with Python 3.5.3.

Python 3.1.1 string to hex

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