need help understanding: converting text to binary

[Eli the Bearded]

In comp.lang.python, Chris Angelico  <rosuav at gmail.com> wrote:
> Have you checked to see if Python can already do this? You mention

I'm sure there's a library already. I'm trying to mix library usage with
my own code to get practice writing in python. In this case, I want code
to deal with MIME encoding in email headers. I turned to a library for
the base64 part and translated C code I once wrote for the
quoted-printable part. I was struck by how complicated it seems to be to
generate binary blobs in python, which makes me think I'm not getting
something.

>> Is there a more python-esque way to convert what should be plain ascii
> What does "plain ASCII" actually mean, though?

ASCII encoded binary data. ASCII is code points that fit in 7-bits
comprising the characters found on a typical 1970s US oriented
typewriter plus a few control characters.

>> into a binary "bytes" object? In the use case I'm working towards the
>> charset will not be ascii or UTF-8 all of the time, and the charset
>> isn't the responsibility of the python code. Think "decode this if
>> charset matches user-specified value, then output in that same charset;
>> otherwise do nothing."
> I'm not sure what this means,

If the terminal expects this encoding, then decode the ASCII transport
encoding and show the raw stream. If the terminal doesn't expect this
encoding, do not decode. Python should be treating it as a a binary
stream, and doesn't need to understand the encoding itself.

> but I would strongly recommend just
> encoding and decoding regardless. Use text internally and bytes at the
> outside.

That feels entirely wrong. I don't know what b'\x9A' means without
knowing the character set and character encoding. If the encoding is a
multibyte one, b'\x9A' doesn't mean anything on its own. That's why I
want to treat it as binary.

Elijah
------
thinking of an array of "unsigned char" not of characters