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Not to revive the Unicode wars again, but a big portion of Python 3's disaster transition to Unicode wasn't caused by "strings being surprisingly hard", but mor

Not to revive the Unicode wars again, but a big portion of Python 3's disaster transition to Unicode wasn't caused by "strings being surprisingly hard", but more rather the Python 3 team having chosen an unworkable text model which multiple people (including me, way back in 2005) all said wouldn't work in practice. Our hard-earned experience was ignored, and it took a long time for future Python editions to eat crow and roll back their mistakes. A large part of why Python 3.6 is a better port target than 3.0 is because they slowly and silently stepped away from their very strong opinions about "what is text", and "what is bytes", and what each of those things meant. Even back when the model was debated, it was clear that the operations the core maintainers cared about (manipulation of individual codepoints [0]) was a dead-end, as the Unicode Standards committee was just about realizing that codepoints weren't an ideal unit, and grapheme clusters were added to the spec. (my dates might be a bit off here, it's all a blur I've mostly forgotten) Python 3.0 was released as basically a completely nonfunctional piece of software. You basically couldn't write anything that touched a binary file in it. The built-in zipfile module, I remember, crashed if you tried to store or load a binary file stored inside a .zip, the only tests at the time stored .txt files, and the bug wasn't fixed for a long time. I remember others having troubles with the email and mime modules, though I didn't have any code that worked with those, personally. I had left the community by that point, but I have heard tales of the mountains Armin Ronacher had to move in order to add the u'' prefix back to Python 3; the core team was against it, instead believing that if 2to3 wasn't working for people, it should be fixed. Alice Bevan–McGregor spent years making a version of the WSGI specification that worked with Python 3's text model. We honestly could have shaved 5-6 years off of that disaster if they had just listened to the community; pretty much every opinion we had shared eventually came true, and the Python 3 text model these days is in a very different, and much healthier, place. [0] One of their major strongholds was that they really needed O(1) indexing of codepoints (it wasn't clear why this was a priority, and I remember arguing that wanting this is a sign of poorly written code). I think in Python 3.8 they finally caved on this, with a PEP and an implementation that can use UTF-16 or UTF-8 internally.

deleted 5y ago
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cygx 5y ago
as the Unicode Standards committee was just about realizing that codepoints weren't an ideal unit Where 'just about' means 1996 at the latest, the release of Unicode 2.0 (cf chapter 5 [1], p. 21, Character Boundaries). [1] http://www.unicode.org/versions/Unicode2.0.0/ch05.pdf http://www.unicode.org/versions/Unicode2.0.0/ch05.pdf
oblvious-earth 5y ago
I'd super appreciate if you have sources (mail archive links or whatever), I'd love to read through Python history stuff like this and the PEP you were referring to? (read through the release notes and couldn't find anything, maybe it relates to PEP 538 in Python 3.7?) It's pretty clear that there were a lot of mistakes in the Python 2 to 3 transition, I'm certainly not trying to defend every choices of the developers.
- Jasper_ 5y ago
  The PEP I was thinking of was actually PEP-393 [0], which was done for Python 3.3 (well, I did say I mostly left the community, and that my dates were probably wrong). It seems it didn't include UTF-8 as a representation; only Latin-1 and UCS-2, and it seems like it only picks a representation if it can maintain the O(1) indexing property. So I was wrong on that one, I guess that's the one thing they haven't given up on :/ As for the rest, I'll see if I can dig up some logs, but a lot of the discussion I was involved in took place on IRC, and my logs were lost a few server wipes ago. You might find some old posts of mine on python-ideas. I've been planning on making a fuller blog post on why I think Python's text model is the wrong one, but Manish has a very good post [1] which covers most of the reason. Basically, Unicode code points don't net you anything over bytes other than O(1) indexing, which is completely useless, and in fact, is in many ways a worse representation. There is no operation where having a list of Unicode code points helps you more than having a list of bytes; well, one that isn't completely broken in practice. More drastically, the team wanting "Unicode everywhere" meant forcing things that clearly weren't Unicode into Unicode. File paths have not been valid Unicode on any popular system. Windows uses its "UTF-16" which is really more UCS-2 and allows unpaired surrogates, and POSIX says node names are bytes but cannot use ASCII NUL or /. These limitations were hit days into the prototyping process on real-world use cases, which is why there's an algorithm to shove arbitrary binary data into unpaired surrogate characters (see PEP-383 [2]), to be used on file paths. This should have blew a huge hole in the whole scheme, but they pushed onwards. The utopian future of "Unicode everywhere" was more important than dealing with the practical reality of existing systems. Similar things happened with console output, where it's now assumed that LANG will be set correctly. But no, when I ssh into a server in Japan that's set to use EUC-JP, Python will output EUC-JP-encoded bytes, which gets shovelled over ssh as bytes, which the terminal emulator on my laptop misinterprets as UTF-8. Yes, I know ssh is supposed to tunnel certain LANG envvars as well. No, I don't remember why it didn't in this case. But a lot of people were hitting this, that in Python 3.7 they finally added UTF-8 mode (PEP-450 [3]). There's still a lot of people for whom this general "Unicode console" idea breaks [4] [5]. Pretty much every part of the standard library was riddled with bugs when they rolled this out (as mentioned, I hit bugs in zipfile, others found bugs in email/mime). For a long time, the only way to know if handed a file-like object is going to be in bytes or not was isinstance(file.read(0), bytes), which is generally ugly, so a lot of modules didn't support bytes even when they should have. Practically everything after has been walking back this text model in favor of something where bytes and str are not even that different anymore. Python 3.5 brought with it PEP-461 [5], which added % formatting back to bytes (after a very long and very tiring discussion with the core maintainers [6]). I could go on and find more PEPs, but I'm done for now. [0] https://www.python.org/dev/peps/pep-0393/ https://www.python.org/dev/peps/pep-0393/ [1] https://manishearth.github.io/blog/2017/01/14/stop-ascribing-meaning-to-unicode-code-points/ https://manishearth.github.io/blog/2017/01/14/stop-ascribing... [2] https://www.python.org/dev/peps/pep-0383/ https://www.python.org/dev/peps/pep-0383/ [3] https://www.python.org/dev/peps/pep-0540/ https://www.python.org/dev/peps/pep-0540/ [4] On POSIX system, https://stackoverflow.com/questions/11741574/how-to-print-utf-8-encoded-text-to-the-console-in-python-3 https://stackoverflow.com/questions/11741574/how-to-print-ut... [5] On Windows, https://stackoverflow.com/questions/17918746/print-unicode-string-to-console-ok-but-fails-when-redirect-to-a-file-how-to-fix https://stackoverflow.com/questions/17918746/print-unicode-s... [5] https://www.python.org/dev/peps/pep-0461/ https://www.python.org/dev/peps/pep-0461/ [6] https://bugs.python.org/issue3982 https://bugs.python.org/issue3982
matheusmoreira 5y ago
> the operations the core maintainers cared about (manipulation of individual codepoints [0]) was a dead-end, as the Unicode Standards committee was just about realizing that codepoints weren't an ideal unit, and grapheme clusters were added to the spec. Can you please expand on this? I thought the problems with Python's new text model were due to backwards incompatibiltiy.
- Jasper_ 5y ago
  The Python developers original plan for the new text model of Python 3 was an expansion of the text model introduced a bit into Python 2. Python 2 has two types: str and unicode. str is a sequence of bytes, and unicode is a sequence of Unicode code points. An unfortunate model, but an understandable one. The difficult part was that since unicode was introduced into Python 2 some time after 2.0, they needed backwards compatibility with existing code, and thus decided that any time an operation wanted unicode and received str, the runtime would automatically decode from str to unicode, and vice versa. This implicit decode/encode became a large hassle, so the aim of Python 3 was to remove it. Unfortunately, while the developers removed the implicit encode/decode in Python 3, they also made the gulf between str and unicode (now called bytes and str) much larger, removing large swaths of useful functionality from bytes, and doubling down on the Unicode code points nature of the new unicode type, despite it being very apparent by then that this was not a good text model to base a language on anymore. Backwards compatibility was a large issue indeed, but IMO they broke backwards compatibility all to introduce a subpar stricter text model that delivered on far fewer promises than tney were hoping, and in my opinion is worse than Python 2's text model. A more reasonable approach can be found in other languages, which allow iterating over sequences of byte strings by iterating on the fly. Swift, Rust and Go all get this more correct.
ngrilly 5y ago
Exactly this. I still remember all of these pain points. It's one of the main reasons why my team moved to Go.

deleted 5y ago

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cygx 5y ago

as the Unicode Standards committee was just about realizing that codepoints weren't an ideal unit Where 'just about' means 1996 at the latest, the release of Unicode 2.0 (cf chapter 5 [1], p. 21, Character Boundaries). [1] http://www.unicode.org/versions/Unicode2.0.0/ch05.pdf http://www.unicode.org/versions/Unicode2.0.0/ch05.pdf

oblvious-earth 5y ago

I'd super appreciate if you have sources (mail archive links or whatever), I'd love to read through Python history stuff like this and the PEP you were referring to? (read through the release notes and couldn't find anything, maybe it relates to PEP 538 in Python 3.7?) It's pretty clear that there were a lot of mistakes in the Python 2 to 3 transition, I'm certainly not trying to defend every choices of the developers.

Jasper_ 5y ago
The PEP I was thinking of was actually PEP-393 [0], which was done for Python 3.3 (well, I did say I mostly left the community, and that my dates were probably wrong). It seems it didn't include UTF-8 as a representation; only Latin-1 and UCS-2, and it seems like it only picks a representation if it can maintain the O(1) indexing property. So I was wrong on that one, I guess that's the one thing they haven't given up on :/ As for the rest, I'll see if I can dig up some logs, but a lot of the discussion I was involved in took place on IRC, and my logs were lost a few server wipes ago. You might find some old posts of mine on python-ideas. I've been planning on making a fuller blog post on why I think Python's text model is the wrong one, but Manish has a very good post [1] which covers most of the reason. Basically, Unicode code points don't net you anything over bytes other than O(1) indexing, which is completely useless, and in fact, is in many ways a worse representation. There is no operation where having a list of Unicode code points helps you more than having a list of bytes; well, one that isn't completely broken in practice. More drastically, the team wanting "Unicode everywhere" meant forcing things that clearly weren't Unicode into Unicode. File paths have not been valid Unicode on any popular system. Windows uses its "UTF-16" which is really more UCS-2 and allows unpaired surrogates, and POSIX says node names are bytes but cannot use ASCII NUL or /. These limitations were hit days into the prototyping process on real-world use cases, which is why there's an algorithm to shove arbitrary binary data into unpaired surrogate characters (see PEP-383 [2]), to be used on file paths. This should have blew a huge hole in the whole scheme, but they pushed onwards. The utopian future of "Unicode everywhere" was more important than dealing with the practical reality of existing systems. Similar things happened with console output, where it's now assumed that LANG will be set correctly. But no, when I ssh into a server in Japan that's set to use EUC-JP, Python will output EUC-JP-encoded bytes, which gets shovelled over ssh as bytes, which the terminal emulator on my laptop misinterprets as UTF-8. Yes, I know ssh is supposed to tunnel certain LANG envvars as well. No, I don't remember why it didn't in this case. But a lot of people were hitting this, that in Python 3.7 they finally added UTF-8 mode (PEP-450 [3]). There's still a lot of people for whom this general "Unicode console" idea breaks [4] [5]. Pretty much every part of the standard library was riddled with bugs when they rolled this out (as mentioned, I hit bugs in zipfile, others found bugs in email/mime). For a long time, the only way to know if handed a file-like object is going to be in bytes or not was isinstance(file.read(0), bytes), which is generally ugly, so a lot of modules didn't support bytes even when they should have. Practically everything after has been walking back this text model in favor of something where bytes and str are not even that different anymore. Python 3.5 brought with it PEP-461 [5], which added % formatting back to bytes (after a very long and very tiring discussion with the core maintainers [6]). I could go on and find more PEPs, but I'm done for now. [0] https://www.python.org/dev/peps/pep-0393/ https://www.python.org/dev/peps/pep-0393/ [1] https://manishearth.github.io/blog/2017/01/14/stop-ascribing-meaning-to-unicode-code-points/ https://manishearth.github.io/blog/2017/01/14/stop-ascribing... [2] https://www.python.org/dev/peps/pep-0383/ https://www.python.org/dev/peps/pep-0383/ [3] https://www.python.org/dev/peps/pep-0540/ https://www.python.org/dev/peps/pep-0540/ [4] On POSIX system, https://stackoverflow.com/questions/11741574/how-to-print-utf-8-encoded-text-to-the-console-in-python-3 https://stackoverflow.com/questions/11741574/how-to-print-ut... [5] On Windows, https://stackoverflow.com/questions/17918746/print-unicode-string-to-console-ok-but-fails-when-redirect-to-a-file-how-to-fix https://stackoverflow.com/questions/17918746/print-unicode-s... [5] https://www.python.org/dev/peps/pep-0461/ https://www.python.org/dev/peps/pep-0461/ [6] https://bugs.python.org/issue3982 https://bugs.python.org/issue3982

matheusmoreira 5y ago

> the operations the core maintainers cared about (manipulation of individual codepoints [0]) was a dead-end, as the Unicode Standards committee was just about realizing that codepoints weren't an ideal unit, and grapheme clusters were added to the spec. Can you please expand on this? I thought the problems with Python's new text model were due to backwards incompatibiltiy.

Jasper_ 5y ago
The Python developers original plan for the new text model of Python 3 was an expansion of the text model introduced a bit into Python 2. Python 2 has two types: str and unicode. str is a sequence of bytes, and unicode is a sequence of Unicode code points. An unfortunate model, but an understandable one. The difficult part was that since unicode was introduced into Python 2 some time after 2.0, they needed backwards compatibility with existing code, and thus decided that any time an operation wanted unicode and received str, the runtime would automatically decode from str to unicode, and vice versa. This implicit decode/encode became a large hassle, so the aim of Python 3 was to remove it. Unfortunately, while the developers removed the implicit encode/decode in Python 3, they also made the gulf between str and unicode (now called bytes and str) much larger, removing large swaths of useful functionality from bytes, and doubling down on the Unicode code points nature of the new unicode type, despite it being very apparent by then that this was not a good text model to base a language on anymore. Backwards compatibility was a large issue indeed, but IMO they broke backwards compatibility all to introduce a subpar stricter text model that delivered on far fewer promises than tney were hoping, and in my opinion is worse than Python 2's text model. A more reasonable approach can be found in other languages, which allow iterating over sequences of byte strings by iterating on the fly. Swift, Rust and Go all get this more correct.

ngrilly 5y ago

Exactly this. I still remember all of these pain points. It's one of the main reasons why my team moved to Go.