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the stupid encoding problem to stdout

Chris Angelico rosuav at gmail.com
Fri Jun 10 18:07:04 EDT 2011 
2011/6/11 Sérgio Monteiro Basto <sergiomb at sapo.pt>:
> ok after thinking about this, this problem exist because Python want be
> smart with ttys

The *anomaly* (not problem) exists because Python has a way of being
told a target encoding. If two parties agree on an encoding, they can
send characters to each other. I had this discussion at work a while
ago; my boss was talking about being "binary-safe" (which really meant
"8-bit safe"), while I was saying that we should support, verify, and
demand properly-formed UTF-8. The main significance is that agreeing
on an encoding means we can change the encoding any time it's
convenient, without having to document that we've changed the data -
because we haven't. I can take the number "twelve thousand three
hundred and forty-five" and render that as a string of decimal digits
as "12345", or as hexadecimal digits as "3039", but I haven't changed
the number. If you know that I'm giving you a string of decimal
digits, and I give you "12345", you will get the same number at the
far side.

Python has agreed with stdout that it will send it characters encoded
in UTF-8. Having made that agreement, Python and stdout can happily
communicate in characters, not bytes. You don't need to explicitly
encode your characters into bytes - and in fact, this would be a very
bad thing to do, because you don't know _what_ encoding stdout is
using. If it's expecting UTF-16, you'll get a whole lot of rubbish if
you send it UTF-8 - but it'll look fine if you send it Unicode.

Chris Angelico
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