How to convert a string to bytes with hexadecimal representation in Python?

I am a very beginner at Python. I have a string that is “TEST00000001” and its length is 12. I want to convert this string to a byte with a hexadecimal representation like this b’x54x45x53x54x30x30x30x30x3030x30x31′. As you can see, the length of the two objects has not changed.

So far, I am successfully converting my string to bytes. But the length of converted bytes is 24 instead of 12.

Here is what I’ve done so far:

sample_string = "TEST00000001"
output = ''.join(hex(ord(character_index))[2:] for character_index in sample_string)
hex_bytes = bytes(output, 'ascii')
print(hex_bytes)  # Output of this line is: b'544553543030303030303031'
print(len(hex_bytes))  # Length of my output is: 24

Can someone help me about converting my string to a byte object (in hex representation) without changing its length?

Answer

To convert a string into bytes in Python, use bytes directly on the string. Don’t call ord or hex on the characters:

hex_string2 = "TEST00000001"
byte_data = bytes(hex_string2, 'ascii')
print(len(byte_data))
# 12

And the output is indeed the same as b'x54x45x53x54x30x30x30x30x30x30x30x31':

byte_data == b'x54x45x53x54x30x30x30x30x30x30x30x31'
# True

---

By contrast, if your input is a string of bytes in padded hexadecimal representation, you need to decode that representation (e.g. using binascii):

import binascii
binascii.unhexlify(b'544553543030303030303031')
# b'TEST00000001'

Or codecs:

import codecs
codecs.decode('544553543030303030303031', 'hex')
# b'TEST00000001'