Comment by oefrha | Hacker News Reader

Comment by oefrha | Hacker News Reader

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> I've found it excruciatingly difficult to write Python code that handles non-ASCII stdio correctly, especially one that might display on a terminal, especially a portable manner, and it didn't get better in Python 3.

I've been doing just that in Python 3 for half a decade at least -- got a fairly popular open source CLI application that hasn't seen a Unicode complaint for years. It doesn't come for free on all possible configurations (yeah, every developer with a wide enough userbase has seen the dreaded "'ascii' codec can't encode characters in position ...: ordinal not in range" at some point) but it's definitely not "excruciatingly difficult". Bad things only happen sys.stdout.encoding isn't utf-8, which is rare on * nix systems -- fixed by setting PYTHONIOENCODING or setting locale to * .UTF-8. Encoding on windows is always a headache (not specific to Python at all) but somehow we seemed to have managed to steer clear too. Anyway, just check sys.stdout.encoding.

Meanwhile, this article is about problems that arise when you have garbage filenames that are neither Unicode nor whatever Microsoft's encoding; I wouldn't expect the average user to deal with files like that in day-to-day usage.

> Bad things only happen sys.stdout.encoding isn't utf-8

Yes, so your code will break when the caller or user sets it to something else.

> which is rare on * nix systems

"UNIX only" is not exactly what I meant by "portable"...

> It doesn't come for free but it's definitely not "excruciatingly difficult".

It's not when you're ignoring the difficult parts!

> Encoding on windows is always a headache (not specific to Python at all)

It's a headache in Windows, but in some cases encoding is worse in Python 3. Sadly I've never sat down to make a library of all the examples I come across, but here's one:

Try predicting what this shell script should print on each platform. (It's Bash/Batch cross-compatible, so once you tell me your prediction, try running in both.)

  (python2 -c "import sys; sys.stdout.write('\xDD')" && python3 -c "import sys; sys.stdout.buffer.write(b'\xDD'); sys.stdout.write('\xDD')") > Temp.bin && python3 -c "import binascii; print(binascii.hexlify(open('Temp.bin', 'rb').read()).decode('ascii'))" && rm Temp.bin

> Yes, so your code will break when the caller or user sets it to something else.

No, it will break when the encoding is set to something where the output text simply can't be encoded. There's simply no such thing as “” in the ASCII locale, or the C locale, so when you try to print those you get an encoding error; if the encoding is set to cp1252 it would be fine.

If you don't want to encode text according to user's preferred encoding, just encode as utf-8 regardless and write the bytes. Let me say this again: if you want to print text, print text; if you want to print a byte stream, print a byte stream. Python3 doesn't make this trivial but it's also not terribly hard.

But by printing utf-8 byte stream under all scenarios, you would be conveniently ignoring the fact that default console encoding on Windows is cp437, not cp65001, so non-ASCII parts of the utf-8 byte stream would be garbled on Windows consoles by default. (And I see garbled Unicode filenames from programs written in other languages all too often when I'm on a Windows console.) It's a damned if you do, damned if you don't situation. Interestingly, the default now is utf-8 on Windows consoles, unless PYTHONLEGACYWINDOWSSTDIO is set. They probably decided that printing (the occasional) garbage is better than correctness.

> Try predicting what this shell script should print on each platform.

Again, not surprising when you realize the default encoding on (en_US) Windows is cp1252. If you want to write a byte 0xdd, don't use '\xDD' which is U+00DD which of course is encoded differently in utf-8 (0xc3 0x9d) and cp1252 (0xdd).

> Again, not surprising when you realize the default encoding on (en_US) Windows is cp1252.

By "the encoding" you're referring to PYTHONIOENCODING, right?

Somehow PYTHONIOENCODING is "not specific to Python at all"?

PYTHONIOENCODING is an override env var you can set. cp1252 being the default on Windows is of course not Python-specific, it’s convention set by Microsoft. In fact, you do realize cp1252 aka Latin-1 was even the default encoding used by the HTML spec before the advent of HTML5 (postdates Python3)? Creators of Python3 certainly didn’t set this default to mess with you.

No, this is just insane Python behavior. There's clearly nothing in the Windows I/O path that's doing this, and if it's a "convention", it's not even one that Python 2 has followed!

PHP doesn't do it this way:

  php -r "echo json_decode(chr(34).'\u00DD'.chr(34));"

Ruby doesn't do it this way either:

  ruby -e "puts \"\u00DD\""

Neither does MSYS2's Bash:

  printf '\u00DD'

Neither does Node.js:

  node --eval="process.stdout.write('\u00DD');"

Hell, even Python 2's behavior of raising an error is more sane than just encoding in cp1252 silently and expecting every developer to somehow know the resulting byte sequence is going to be different on each platform:

  python3 -c "print(u'\u00DD')"

Obviously, I'm not the only one who thinks that whatever this (ancient?) so-called "convention" is, it's actively harmful enough to avoid in 2019.

And as if that's not enough, that's not even the end of it. Even literally writing a string to a file (with no console or stdio in between!!) ends up producing a completely different file depending on which platform the code is run on:

  python3 -c "open('Temp.bin', 'w+').write(u'\u00DD')" && xxd Temp.bin && rm Temp.bin

How is any programmer supposed to deal with this insanity? A program writes to a file, but produces files with completely different contents depending on the platform? Heaven help you if you try to interacting with a program in another language. At least with newlines, as painful as they are, most people know and recognize how to deal with them. But dealing with that mess is enough, and not a reason to make the situation even worse?! It's almost as if they took the CRLF issue and then went "Hmm, that's not fair to CR or LF, we need to do this to even more characters."

Somehow we have all this nonsense in the name of "fixing" strings from Python 2. Instead of finding a better convention or at least leaving the existing behavior alone, Python 3—which is intended to let people write cross-platform code!—actively embraced it and botched Python 2's safe behavior, making programs produce garbled output completely silently... and blaming it on the stupid developer for trying to write a broken cross-platform program without first getting a PhD on the history of Code Pages on Windows.

I think the issue comes from PHP magic with non-ASCII values. PHP tries to guess and never fails.

Python instead doesn't do this for you.

Anyway, some non-english speaker countries developers feel like programming language developers still have different encodings as second citizens like this was the sixties.

I hope this changes some time in the future although 10 years ago I already hoped for today to be that future.

Let me quote the sys.stdout/sys.stderr encoding rules:

> The character encoding is platform-dependent. Non-Windows platforms use the locale encoding (see locale.getpreferredencoding()).

> On Windows, UTF-8 is used for the console device. Non-character devices such as disk files and pipes use the system locale encoding (i.e. the ANSI codepage). Non-console character devices such as NUL (i.e. where isatty() returns True) use the value of the console input and output codepages at startup, respectively for stdin and stdout/stderr. This defaults to the system locale encoding if the process is not initially attached to a console.

> The special behaviour of the console can be overridden by setting the environment variable PYTHONLEGACYWINDOWSSTDIO before starting Python. In that case, the console codepages are used as for any other character device.

> Under all platforms, you can override the character encoding by setting the PYTHONIOENCODING environment variable before starting Python or by using the new -X utf8 command line option and PYTHONUTF8 environment variable. However, for the Windows console, this only applies when PYTHONLEGACYWINDOWSSTDIO is also set.

https://docs.python.org/3/library/sys.html#sys.stdout

locale.getpreferredencoding doc is vague

> Return the encoding used for text data, according to user preferences. User preferences are expressed differently on different systems, and might not be available programmatically on some systems, so this function only returns a guess.

https://docs.python.org/3/library/locale.html#locale.getpref...

But on *nix it's basically based on the second part of your locale. If it's anything.UTF-8 (and your terminal talks UTF-8) there won't be a problem. If you set your locale to C or something.ASCII or whatever you can't really blame Python for trying to encode the output according to what you claim to prefer.

I fail to see how you can "guess" the terminal's expected encoding otherwise.

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