Say that I have a 4 character string, and I want to convert this string into a byte array where each character in the string is translated into its hex equivalent. e.g.

str = "ABCD"

I'm trying to get my output to be

array('B', [41, 42, 43, 44])

Is there a straightforward way to accomplish this?

1

9 Answers

encode function can help you here, encode returns an encoded version of the string

In [44]: str = "ABCD"
In [45]: [elem.encode("hex") for elem in str]
Out[45]: ['41', '42', '43', '44']

or you can use array module

In [49]: import array
In [50]: print array.array('B', "ABCD")
array('B', [65, 66, 67, 68])

2

Just use a bytearray() which is a list of bytes.

Python2:

s = "ABCD"
b = bytearray()
b.extend(s)

Python3:

s = "ABCD"
b = bytearray()
b.extend(map(ord, s))

By the way, don't use str as a variable name since that is builtin.

7

An alternative to get a byte array is to encode the string in ascii: b=s.encode('ascii').

2

This works for me (Python 2)

s = "ABCD"
b = bytearray(s)
# if you print whole b, it still displays it as if its original string
print b
# but print first item from the array to see byte value
print b[0]

Reference:

This work in both Python 2 and 3:

>>> bytearray(b'ABCD')
bytearray(b'ABCD')

Note string started with b.

To get individual chars:

>>> print("DEC HEX ASC")
... for b in bytearray(b'ABCD'):
... print(b, hex(b), chr(b))
DEC HEX ASC
65 0x41 A
66 0x42 B
67 0x43 C
68 0x44 D

Hope this helps

Depending on your needs, this can be one step or two steps

1. use encode() to convert string to bytes, immutable
2. use bytearray() to convert bytes to bytearray, mutable

s="ABCD"
encoded=s.encode('utf-8')
array=bytearray(encoded)

The following validation is done in Python 3.7

>>> s="ABCD"
>>> encoded=s.encode('utf-8')
>>> encoded
b'ABCD'
>>> array=bytearray(encoded)
>>> array
bytearray(b'ABCD')

s = "ABCD"
from array import array
a = array("B", s)

If you want hex:

print map(hex, a)

1

Since none of the answers is producing exactly array('B', [41, 42, 43, 44]) and the answer by avasal fails in Python 3, I post here my alternative:

import array
s = 'ABCD'
a = array.array('B', [ord(c) for c in s])
print(a)

which prints

array('B', [65, 66, 67, 68])

Note that 65-68 is the correct ASCII for "ABCD".

for python 3 it worked for what @HYRY posted. I needed it for a returned data in a dbus.array. This is the only way it worked

s = "ABCD"

from array import array

a = array("B", s)

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