How can I encode string data (convert to bytes) in Python 3.7

Question

i have a problem.

i get data like:

hex_num='0EE6'
data_decode=str(codecs.decode(hex_num, 'hex'))[(0):(80)]
print(data_decode)
>>>b'\x0e\xe6'

And i want encode this like:

data_enc=str(codecs.encode(data_decode, 'hex'))[(2):(6)]
print(str(int(data_enc,16)))
>>>TypeError: encoding with 'hex' codec failed (TypeError: a bytes-like object is required, not 'str')

If i wrote this:

data_enc=str(codecs.encode(b'\x0e\xe6', 'hex'))[(2):(6)]
print(str(int(data_enc,16)))
>>>3814

It will retrun number what i want (3814)

Please help.

DapperDuck · Accepted Answer · 2021-01-03 16:12:59Z

1

You can remove the quotation marks like this: data = b'\x0e\xe6'

The Python 3 documentation states:

Bytes literals are always prefixed with 'b' or 'B'; they produce an instance of the bytes type instead of the str type. They may only contain ASCII characters; bytes with a numeric value of 128 or greater must be expressed with escapes.

When b is within a string, it will not behave like a string literal prefix, so you have to remove the quotations for the literal to work, and convert the text to bytes directly.

Corrected code:

import codecs
data = b'\x0e\xe6'
data_enc=str(codecs.encode(data, 'hex'))[(2):(6)]
print(str(int(data_enc,16)))

Output:

edited Jan 3, 2021 at 16:12

answered Jan 3, 2021 at 16:03

DapperDuck

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2 Comments

astqx Over a year ago

It would be more beneficial to OP if you could explain the reason of that as well

DapperDuck Over a year ago

Please don't edit the question, that can make it difficult for future users. If you want to ask another question, post a new question, don't edit the current one!

ukBaz · Accepted Answer · 2021-01-10 07:51:32Z

0

To change from a hex string to binary data, then using binascii.unhexlify is a convenient method. e.g.:

>>> hex_num='0EE6'
>>> import binascii
>>> binascii.unhexlify(hex_num)
b'\x0e\xe6'

Then to convert the binary data to an integer, using int.from_bytes allows you control over the endianness of the data and if it signed. e.g:

>>> bytes_data = b'\x0e\xe6'
>>> int.from_bytes(bytes_data, byteorder='little', signed=False)
58894
>>> int.from_bytes(bytes_data, byteorder='big', signed=False)
3814

answered Jan 10, 2021 at 7:51

ukBaz

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