[Python-Dev] email package status in 3.X (original) (raw)

Stephen J. Turnbull turnbull at sk.tsukuba.ac.jp
Mon Jun 21 19:58:22 CEST 2010

P.J. Eby writes:

Note too that this is an argument for symmetry in wrapping the inputs and outputs, so that the code doesn't have to "know" what it's dealing with!

and

After all, right now, if a stdlib function might return bytes or unicode depending on runtime conditions, I can't even hardcode an .encode() call -- it would fail if the return type is a bytes.

I'm lost. What stdlib functions are you talking about whose return type depends on runtime conditions, and what runtime conditions? What do you mean by "wrapping"?

The only times I've run into str/bytes nondeterminancy is when I've mixed str/bytes myself, and passed them into functions that are type-identities (str -> str, bytes -> bytes), which then appear to give a nondeterministic result. It's a deterministic bug, though, always mine.

It's One Obvious Way that I want, but some people seem to be arguing that the One Obvious Way is to Think Carefully About It Every Time -- and that seems to violate the "Obvious" part, IMO. ;-)

Nick alluded to the The One Obvious Way as a change in architecture.

Specifically: Decode all bytes to typed objects (str, images, audio, structured objects) at input. Do no manipulations on bytes ever except decode and encode (both to text, and to special-purpose objects such as images) in a program that does I/O. (Obviously image manipulation libraries etc will have to operate on bytes, but they should have no functions that consume bytes except constructors a la bytes.decode() for text, and no functions that produce bytes except the output serializers that write files and the like, a la str.encode().) Encode back to bytes on output.

Yes, this is tedious if you live in an ASCII world, compared to using bytes as characters. However, it works for the rest of us, which the old style doesn't.

As for "Think Carefully About It Every Time", that is required only in Porting Programs That Mix Operation On Bytes With Operation On Str. If you write programs from scratch, however, the decode-process-encode paradigm quickly becomes second nature.

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