How do I write a single 8-bit byte to a file?

[bowlofred]

Those aren't ints. You describe the bit at the end as "concatenated 8-bit bytes", but I'm guessing they're actually hexadecimal strings, so each character represents a 4-bit value.

You can create a byte object directly from a hex string like this:

>>> nmbr = bytes.fromhex("0102030405")
>>> nmbr
b'\x01\x02\x03\x04\x05'
>>> len(nmbr)
5

Since you've opened the file as binary and you have a bytes object, you can write it directly. There's no encoding necessary here.