*Hi Folks,Cc: Rebecca, pytypeThis is Adam Cataldo; I’m the engineering manager for the Python team at Google. Rebecca Chen, our lead pytype https://github.com/google/pytype contributor, and I are interested in helping finalize PEP 484 if possible. To that end, we wanted to find out what technical issues the PEP 484 authors feel they still need to finalize. We also wanted to know how we can help.We have a large Python code base at Google, and may be able to use this to help resolve current incomplete definitions, by collecting data on how types are used. We also have a couple ambiguities that we’d love to get closure on: - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.- The relationship between unicode and typing.Text in Python 2 has been a recurring source of confusion for our users. Especially since we contributed https://github.com/python/peps/pull/302 to the current state of affairs, we’d like to figure out how to establish clarity here.Thoughts?Thanks,Adam*
On Mon, 16 Jul 2018 at 10:32 Adam Cataldo via Python-Dev < python-dev@python.org> wrote:
*Hi Folks,Cc: Rebecca, pytypeThis is Adam Cataldo; I’m the engineering manager for the Python team at Google. Rebecca Chen, our lead pytype https://github.com/google/pytype contributor, and I are interested in helping finalize PEP 484 if possible. To that end, we wanted to find out what technical issues the PEP 484 authors feel they still need to finalize. We also wanted to know how we can help.We have a large Python code base at Google, and may be able to use this to help resolve current incomplete definitions, by collecting data on how types are used. We also have a couple ambiguities that we’d love to get closure on: - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.*
What specifically do you want beyond https://www.python.org/dev/peps/pep-0484/#stub-files?
* - The relationship between unicode and typing.Text in Python 2 has been a recurring source of confusion for our users. Especially since we contributed https://github.com/python/peps/pull/302 to the current state of affairs, we’d like to figure out how to establish clarity here.Thoughts?*
Do be aware, Adam, that due to Guido's retirement last week people might be a bit preoccupied and so a little slow in responding. But then again Guido just got a bit more free time so he might chime in on this one. ;)
Hi, my name is Teddy Sudol. I work with Adam and Rebecca on pytype.
The explanation of stub files is unclear. The section you linked starts
with, "Stub files are files containing type hints that are only for use by
the type checker, not at runtime." According to
https://www.python.org/dev/peps/pep-0484/#acceptable-type-hints, type hints
may be classes, abstract base classes, types defined in the `types` and
`typing` modules, type variables, type aliases and None. Further in the
section you linked, PEP 484 also states, "Stub files have the same syntax
as regular Python modules," and, "no runtime behavior should be expected of
stub files."
"Have the same syntax as regular Python modules" and "are files containing
type hints" are at odds with each other. This has led to compatibility
issues between Mypy and pytype. For example, `b''` is not a valid type
annotation, but until a month ago, `codecs.pyi` in typeshed used exactly
that:
https://github.com/python/typeshed/commit/6bbf3d89eb9b6c3fd5b0c0f632b2ad9258....
If statements can be useful for things like version checks, but on the
other hand, pyi files aren't supposed to have any runtime behavior.
Additionally, codifying the syntax for pyi files would settle questions
like whether constants should be typed using "x: <type hint>" or "x = ...
# type: <type hint>".
We would like to see a clear statement about the syntax of stub files.
Personally, I think they should be a subset of Python, but I'd also be
happy with an EBNF grammar for them.
-- Teddy
On Mon, Jul 16, 2018 at 11:05 AM Brett Cannon
On Mon, 16 Jul 2018 at 10:32 Adam Cataldo via Python-Dev < python-dev@python.org> wrote:
*Hi Folks,Cc: Rebecca, pytypeThis is Adam Cataldo; I’m the engineering manager for the Python team at Google. Rebecca Chen, our lead pytype https://github.com/google/pytype contributor, and I are interested in helping finalize PEP 484 if possible. To that end, we wanted to find out what technical issues the PEP 484 authors feel they still need to finalize. We also wanted to know how we can help.We have a large Python code base at Google, and may be able to use this to help resolve current incomplete definitions, by collecting data on how types are used. We also have a couple ambiguities that we’d love to get closure on: - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.*
What specifically do you want beyond https://www.python.org/dev/peps/pep-0484/#stub-files?
* - The relationship between unicode and typing.Text in Python 2 has been a recurring source of confusion for our users. Especially since we contributed https://github.com/python/peps/pull/302 to the current state of affairs, we’d like to figure out how to establish clarity here.Thoughts?*
Do be aware, Adam, that due to Guido's retirement last week people might be a bit preoccupied and so a little slow in responding. But then again Guido just got a bit more free time so he might chime in on this one. ;)
-- You received this message because you are subscribed to the Google Groups "pytype" group. To unsubscribe from this group and stop receiving emails from it, send an email to pytype+unsubscribe@googlegroups.com. To post to this group, send email to pytype@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRc... https://groups.google.com/d/msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRcZJF_Azq3g6QFQ2oiAw%40mail.gmail.com?utm_medium=email&utm_source=footer . For more options, visit https://groups.google.com/d/optout.
Thanks Brett and Teddy,
Just so it doesn't get lost in the shuffle as folks dive into details, I'll
re-ask my earlier question about stub files. Assuming there is consensus
that there is ambiguity to resolve in the current definition, is updating
the section on stub files the preferred option? The only alternative I can
think of is to pull this out into a separate PEP. I frankly have no opinion
on what the best way to capture this is. We're happy to help out either way.
On Mon, Jul 16, 2018 at 12:48 PM Teddy Sudol
Hi, my name is Teddy Sudol. I work with Adam and Rebecca on pytype.
The explanation of stub files is unclear. The section you linked starts with, "Stub files are files containing type hints that are only for use by the type checker, not at runtime." According to https://www.python.org/dev/peps/pep-0484/#acceptable-type-hints, type hints may be classes, abstract base classes, types defined in the `types` and `typing` modules, type variables, type aliases and None. Further in the section you linked, PEP 484 also states, "Stub files have the same syntax as regular Python modules," and, "no runtime behavior should be expected of stub files."
"Have the same syntax as regular Python modules" and "are files containing type hints" are at odds with each other. This has led to compatibility issues between Mypy and pytype. For example, `b''` is not a valid type annotation, but until a month ago, `codecs.pyi` in typeshed used exactly that: https://github.com/python/typeshed/commit/6bbf3d89eb9b6c3fd5b0c0f632b2ad9258.... If statements can be useful for things like version checks, but on the other hand, pyi files aren't supposed to have any runtime behavior. Additionally, codifying the syntax for pyi files would settle questions like whether constants should be typed using "x: <type hint>" or "x = ... # type: <type hint>".
We would like to see a clear statement about the syntax of stub files. Personally, I think they should be a subset of Python, but I'd also be happy with an EBNF grammar for them.
-- Teddy
On Mon, Jul 16, 2018 at 11:05 AM Brett Cannon
wrote: On Mon, 16 Jul 2018 at 10:32 Adam Cataldo via Python-Dev < python-dev@python.org> wrote:
*Hi Folks,Cc: Rebecca, pytypeThis is Adam Cataldo; I’m the engineering manager for the Python team at Google. Rebecca Chen, our lead pytype https://github.com/google/pytype contributor, and I are interested in helping finalize PEP 484 if possible. To that end, we wanted to find out what technical issues the PEP 484 authors feel they still need to finalize. We also wanted to know how we can help.We have a large Python code base at Google, and may be able to use this to help resolve current incomplete definitions, by collecting data on how types are used. We also have a couple ambiguities that we’d love to get closure on: - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.*
What specifically do you want beyond https://www.python.org/dev/peps/pep-0484/#stub-files?
* - The relationship between unicode and typing.Text in Python 2 has been a recurring source of confusion for our users. Especially since we contributed https://github.com/python/peps/pull/302 to the current state of affairs, we’d like to figure out how to establish clarity here.Thoughts?*
Do be aware, Adam, that due to Guido's retirement last week people might be a bit preoccupied and so a little slow in responding. But then again Guido just got a bit more free time so he might chime in on this one. ;)
-- You received this message because you are subscribed to the Google Groups "pytype" group. To unsubscribe from this group and stop receiving emails from it, send an email to pytype+unsubscribe@googlegroups.com. To post to this group, send email to pytype@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRc... https://groups.google.com/d/msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRcZJF_Azq3g6QFQ2oiAw%40mail.gmail.com?utm_medium=email&utm_source=footer . For more options, visit https://groups.google.com/d/optout.
As one of the authors of PEP 484, *I* never thought there was an ambiguity here. The intention was for stub files to conform to the same grammar as regular .py files, but with a different interpretation.
"Have the same syntax as regular Python modules" and "are files containing type hints" are at odds with each other.
That depends. *same syntax as regular Python* is normative while *containing type hints* is an informal description of intent. I happen to be somewhat familiar with the situation that lead to this question -- pytype has its own parser for stub files that cannot parse all Python constructs. But claiming that PEP 484 is ambiguous feels wrong, and if we really need to clarify it the only way to go is to make "same syntax as regular Python" more clearly normative. Type checkers should of course feel free ignore everything they don't care about. Regarding the unicode issue, that is indeed unfortunate, and there's a long but inconclusive discussion at https://github.com/python/typing/issues/208. (If you want a longer discussion here please start a new subject.) On Mon, Jul 16, 2018 at 1:02 PM, Adam Cataldo via Python-Dev < python-dev@python.org> wrote:
Thanks Brett and Teddy,
Just so it doesn't get lost in the shuffle as folks dive into details, I'll re-ask my earlier question about stub files. Assuming there is consensus that there is ambiguity to resolve in the current definition, is updating the section on stub files the preferred option? The only alternative I can think of is to pull this out into a separate PEP. I frankly have no opinion on what the best way to capture this is. We're happy to help out either way.
On Mon, Jul 16, 2018 at 12:48 PM Teddy Sudol
wrote: Hi, my name is Teddy Sudol. I work with Adam and Rebecca on pytype.
The explanation of stub files is unclear. The section you linked starts with, "Stub files are files containing type hints that are only for use by the type checker, not at runtime." According to https://www.python.org/dev/peps/pep-0484/#acceptable-type-hints, type hints may be classes, abstract base classes, types defined in the `types` and `typing` modules, type variables, type aliases and None. Further in the section you linked, PEP 484 also states, "Stub files have the same syntax as regular Python modules," and, "no runtime behavior should be expected of stub files."
"Have the same syntax as regular Python modules" and "are files containing type hints" are at odds with each other. This has led to compatibility issues between Mypy and pytype. For example, `b''` is not a valid type annotation, but until a month ago, `codecs.pyi` in typeshed used exactly that: https://github.com/python/typeshed/commit/ 6bbf3d89eb9b6c3fd5b0c0f632b2ad9258cecf15#diff- 5f6f48c425bc0c283784cf5277880c0cL95. If statements can be useful for things like version checks, but on the other hand, pyi files aren't supposed to have any runtime behavior. Additionally, codifying the syntax for pyi files would settle questions like whether constants should be typed using "x: <type hint>" or "x = ... # type: <type hint>".
We would like to see a clear statement about the syntax of stub files. Personally, I think they should be a subset of Python, but I'd also be happy with an EBNF grammar for them.
-- Teddy
On Mon, Jul 16, 2018 at 11:05 AM Brett Cannon
wrote: On Mon, 16 Jul 2018 at 10:32 Adam Cataldo via Python-Dev < python-dev@python.org> wrote:
*Hi Folks,Cc: Rebecca, pytypeThis is Adam Cataldo; I’m the engineering manager for the Python team at Google. Rebecca Chen, our lead pytype https://github.com/google/pytype contributor, and I are interested in helping finalize PEP 484 if possible. To that end, we wanted to find out what technical issues the PEP 484 authors feel they still need to finalize. We also wanted to know how we can help.We have a large Python code base at Google, and may be able to use this to help resolve current incomplete definitions, by collecting data on how types are used. We also have a couple ambiguities that we’d love to get closure on: - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.*
What specifically do you want beyond https://www.python.org/dev/ peps/pep-0484/#stub-files?
* - The relationship between unicode and typing.Text in Python 2 has been a recurring source of confusion for our users. Especially since we contributed https://github.com/python/peps/pull/302 to the current state of affairs, we’d like to figure out how to establish clarity here.Thoughts?*
Do be aware, Adam, that due to Guido's retirement last week people might be a bit preoccupied and so a little slow in responding. But then again Guido just got a bit more free time so he might chime in on this one. ;)
-- You received this message because you are subscribed to the Google Groups "pytype" group. To unsubscribe from this group and stop receiving emails from it, send an email to pytype+unsubscribe@googlegroups.com. To post to this group, send email to pytype@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/ msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRc ZJF_Azq3g6QFQ2oiAw%40mail.gmail.com https://groups.google.com/d/msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRcZJF_Azq3g6QFQ2oiAw%40mail.gmail.com?utm_medium=email&utm_source=footer . For more options, visit https://groups.google.com/d/optout.
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-- --Guido van Rossum (python.org/~guido)
On Mon, Jul 16, 2018 at 1:44 PM Guido van Rossum
As one of the authors of PEP 484, *I* never thought there was an ambiguity here. The intention was for stub files to conform to the same grammar as regular .py files, but with a different interpretation.
"Have the same syntax as regular Python modules" and "are files containing type hints" are at odds with each other.
That depends. *same syntax as regular Python* is normative while *containing type hints* is an informal description of intent.
I happen to be somewhat familiar with the situation that lead to this question -- pytype has its own parser for stub files that cannot parse all Python constructs. But claiming that PEP 484 is ambiguous feels wrong, and if we really need to clarify it the only way to go is to make "same syntax as regular Python" more clearly normative. Type checkers should of course feel free ignore everything they don't care about.
I feel like the "same syntax as regular Python" is too broad a statement. That effectively requires a version specific Python interpreter to execute the files. With at least four different Python static analyzers in existence today, keeping the behavior of all of them consistent is important. Otherwise pyi files will be (are being) created that are analyzer specific and break other type checkers when distributed. ex: We're encountering pyi files with conditional logic in them. I believe we've encountered pyi files with del statements in them? Both of these are a slippery slope towards being turing complete in something that isn't supposed to be code. I don't like this. Interface declarations should not contain logic. If we allow conditions, we need to explicitly define what we do allow in the PEP. (if+else and del? what inputs are allowed for the expression in if statements?). Otherwise at some point someone is going to create a pyi file containing loops, function calls, and generator expressions and expect it to _do_ something. The horror! Lets avoid that. PEP-484 does contain the text, "This also reinforces the notion that no runtime behavior should be expected of stub files." But reinforcing a notion is not what I read as a concrete statement. I'd rather see that say something like, "There must not be any runtime behavior from a stub file. They will be parsed for information, not executed." Wordsmith that all you want, I'm not pedantic enough. :) I expect someone pedantic to happily point out that a def or class or assignment to ... with an annotation is runtime behavior... technically correct, but that isn't how people like me think of them in this context. We use a Pythonic syntax for stubs to be consistent with the language, that doesn't mean they are code. I wrote more than I thought I would here, I'll stop now. :) -gps
Regarding the unicode issue, that is indeed unfortunate, and there's a long but inconclusive discussion at https://github.com/python/typing/issues/208. (If you want a longer discussion here please start a new subject.)
On Mon, Jul 16, 2018 at 1:02 PM, Adam Cataldo via Python-Dev < python-dev@python.org> wrote:
Thanks Brett and Teddy,
Just so it doesn't get lost in the shuffle as folks dive into details, I'll re-ask my earlier question about stub files. Assuming there is consensus that there is ambiguity to resolve in the current definition, is updating the section on stub files the preferred option? The only alternative I can think of is to pull this out into a separate PEP. I frankly have no opinion on what the best way to capture this is. We're happy to help out either way.
On Mon, Jul 16, 2018 at 12:48 PM Teddy Sudol
wrote: Hi, my name is Teddy Sudol. I work with Adam and Rebecca on pytype.
The explanation of stub files is unclear. The section you linked starts with, "Stub files are files containing type hints that are only for use by the type checker, not at runtime." According to https://www.python.org/dev/peps/pep-0484/#acceptable-type-hints, type hints may be classes, abstract base classes, types defined in the `types` and `typing` modules, type variables, type aliases and None. Further in the section you linked, PEP 484 also states, "Stub files have the same syntax as regular Python modules," and, "no runtime behavior should be expected of stub files."
"Have the same syntax as regular Python modules" and "are files containing type hints" are at odds with each other. This has led to compatibility issues between Mypy and pytype. For example, `b''` is not a valid type annotation, but until a month ago, `codecs.pyi` in typeshed used exactly that: https://github.com/python/typeshed/commit/6bbf3d89eb9b6c3fd5b0c0f632b2ad9258.... If statements can be useful for things like version checks, but on the other hand, pyi files aren't supposed to have any runtime behavior. Additionally, codifying the syntax for pyi files would settle questions like whether constants should be typed using "x: <type hint>" or "x = ... # type: <type hint>".
We would like to see a clear statement about the syntax of stub files. Personally, I think they should be a subset of Python, but I'd also be happy with an EBNF grammar for them.
-- Teddy
On Mon, Jul 16, 2018 at 11:05 AM Brett Cannon
wrote: On Mon, 16 Jul 2018 at 10:32 Adam Cataldo via Python-Dev < python-dev@python.org> wrote:
*Hi Folks,Cc: Rebecca, pytypeThis is Adam Cataldo; I’m the engineering manager for the Python team at Google. Rebecca Chen, our lead pytype https://github.com/google/pytype contributor, and I are interested in helping finalize PEP 484 if possible. To that end, we wanted to find out what technical issues the PEP 484 authors feel they still need to finalize. We also wanted to know how we can help.We have a large Python code base at Google, and may be able to use this to help resolve current incomplete definitions, by collecting data on how types are used. We also have a couple ambiguities that we’d love to get closure on: - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.*
What specifically do you want beyond https://www.python.org/dev/peps/pep-0484/#stub-files?
* - The relationship between unicode and typing.Text in Python 2 has been a recurring source of confusion for our users. Especially since we contributed https://github.com/python/peps/pull/302 to the current state of affairs, we’d like to figure out how to establish clarity here.Thoughts?*
Do be aware, Adam, that due to Guido's retirement last week people might be a bit preoccupied and so a little slow in responding. But then again Guido just got a bit more free time so he might chime in on this one. ;)
-- You received this message because you are subscribed to the Google Groups "pytype" group. To unsubscribe from this group and stop receiving emails from it, send an email to pytype+unsubscribe@googlegroups.com. To post to this group, send email to pytype@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRc... https://groups.google.com/d/msgid/pytype/CAP1%3D2W4NxcsSdsiMrh55KhjkwgD0PGRcZJF_Azq3g6QFQ2oiAw%40mail.gmail.com?utm_medium=email&utm_source=footer . For more options, visit https://groups.google.com/d/optout.
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On Mon, Jul 16, 2018 at 2:56 PM, Gregory P. Smith
On Mon, Jul 16, 2018 at 1:44 PM Guido van Rossum
wrote: As one of the authors of PEP 484, *I* never thought there was an ambiguity here. The intention was for stub files to conform to the same grammar as regular .py files, but with a different interpretation.
"Have the same syntax as regular Python modules" and "are files containing type hints" are at odds with each other.
That depends. *same syntax as regular Python* is normative while *containing type hints* is an informal description of intent.
I happen to be somewhat familiar with the situation that lead to this question -- pytype has its own parser for stub files that cannot parse all Python constructs. But claiming that PEP 484 is ambiguous feels wrong, and if we really need to clarify it the only way to go is to make "same syntax as regular Python" more clearly normative. Type checkers should of course feel free ignore everything they don't care about.
I feel like the "same syntax as regular Python" is too broad a statement. That effectively requires a version specific Python interpreter to execute the files. With at least four different Python static analyzers in existence today, keeping the behavior of all of them consistent is important. Otherwise pyi files will be (are being) created that are analyzer specific and break other type checkers when distributed.
it doesn't require an interpreter, just a parser. Is saying it should be syntactically valid Python 3.6 (though emphatically not executable!) still too much?
ex: We're encountering pyi files with conditional logic in them. I believe we've encountered pyi files with del statements in them? Both of these are a slippery slope towards being turing complete in something that isn't supposed to be code. I don't like this. Interface declarations should not contain logic. If we allow conditions, we need to explicitly define what we do allow in the PEP. (if+else and del? what inputs are allowed for the expression in if statements?). Otherwise at some point someone is going to create a pyi file containing loops, function calls, and generator expressions and expect it to _do_ something. The horror! Lets avoid that.
Syntactically, conditional logic *is* part of the spec because of `sys.version_info` and `sys.platform` checks. These are mentioned in PEP 484 (though IIRC they were added at some point). Feel free to ignore `del` statements, but they are valid syntax.
PEP-484 does contain the text, "This also reinforces the notion that no runtime behavior should be expected of stub files." But reinforcing a notion is not what I read as a concrete statement.
I'd rather see that say something like, "There must not be any runtime behavior from a stub file. They will be parsed for information, not executed." Wordsmith that all you want, I'm not pedantic enough. :)
I don't see that as any more precise as what the PEP says. :-) I'd be happy to claim that if the ast module can't parse a .pyi file, it's invalid, otherwise it's valid, except that `# type:` comments are significant and the ast module doesn't preserve those.
I expect someone pedantic to happily point out that a def or class or assignment to ... with an annotation is runtime behavior... technically correct, but that isn't how people like me think of them in this context.
And mypy agrees. :-)
We use a Pythonic syntax for stubs to be consistent with the language, that doesn't mean they are code.
Define "code". To some people HTML is code.
I wrote more than I thought I would here, I'll stop now. :)
It would be nice if the pytype team could articulate the problems they're trying to solve, rather than offering to "help finalize PEP 484". My guess is that their parser for .pyi files only accepts a subset of Python and they're (you're? do you report to Adam?) reluctant to sink more time in that parser -- but I don't think that's my problem. :-) My intention for stubs was exactly what I've been saying in this thread: they must be syntactically valid Python, they are not meant to be executed, and type checkers are free to ignore things they don't need. If that's not sufficiently clear in the way the PEP is currently written, I welcome a PR to the peps repo. If the pytype team wants a different interpretation, the bar is much higher. -- --Guido van Rossum (python.org/~guido)
Hi Guido and all,
Let me try to clarify our (pytype team's) intentions a bit. Our
overall goal is to see PEP 484 finalized, in the interest of having a
definitive type-checking reference to point to and work off of. We're
willing and eager to help with this, if we get some guidance on what
the authors are still trying to finalize and how we can be useful. As
a conversation starter, we offered two issues in which pytype has some
personal stake.
Best,
Rebecca
P.S. Yes, Adam manages Python at Google.
On Mon, Jul 16, 2018 at 3:15 PM Guido van Rossum
On Mon, Jul 16, 2018 at 2:56 PM, Gregory P. Smith
wrote: On Mon, Jul 16, 2018 at 1:44 PM Guido van Rossum
wrote: As one of the authors of PEP 484, *I* never thought there was an ambiguity here. The intention was for stub files to conform to the same grammar as regular .py files, but with a different interpretation.
"Have the same syntax as regular Python modules" and "are files containing type hints" are at odds with each other.
That depends. *same syntax as regular Python* is normative while *containing type hints* is an informal description of intent.
I happen to be somewhat familiar with the situation that lead to this question -- pytype has its own parser for stub files that cannot parse all Python constructs. But claiming that PEP 484 is ambiguous feels wrong, and if we really need to clarify it the only way to go is to make "same syntax as regular Python" more clearly normative. Type checkers should of course feel free ignore everything they don't care about.
I feel like the "same syntax as regular Python" is too broad a statement. That effectively requires a version specific Python interpreter to execute the files. With at least four different Python static analyzers in existence today, keeping the behavior of all of them consistent is important. Otherwise pyi files will be (are being) created that are analyzer specific and break other type checkers when distributed.
it doesn't require an interpreter, just a parser. Is saying it should be syntactically valid Python 3.6 (though emphatically not executable!) still too much?
ex: We're encountering pyi files with conditional logic in them. I believe we've encountered pyi files with del statements in them? Both of these are a slippery slope towards being turing complete in something that isn't supposed to be code. I don't like this. Interface declarations should not contain logic. If we allow conditions, we need to explicitly define what we do allow in the PEP. (if+else and del? what inputs are allowed for the expression in if statements?). Otherwise at some point someone is going to create a pyi file containing loops, function calls, and generator expressions and expect it to _do_ something. The horror! Lets avoid that.
Syntactically, conditional logic *is* part of the spec because of `sys.version_info` and `sys.platform` checks. These are mentioned in PEP 484 (though IIRC they were added at some point).
Feel free to ignore `del` statements, but they are valid syntax.
PEP-484 does contain the text, "This also reinforces the notion that no runtime behavior should be expected of stub files." But reinforcing a notion is not what I read as a concrete statement.
I'd rather see that say something like, "There must not be any runtime behavior from a stub file. They will be parsed for information, not executed." Wordsmith that all you want, I'm not pedantic enough. :)
I don't see that as any more precise as what the PEP says. :-)
I'd be happy to claim that if the ast module can't parse a .pyi file, it's invalid, otherwise it's valid, except that `# type:` comments are significant and the ast module doesn't preserve those.
I expect someone pedantic to happily point out that a def or class or assignment to ... with an annotation is runtime behavior... technically correct, but that isn't how people like me think of them in this context.
And mypy agrees. :-)
We use a Pythonic syntax for stubs to be consistent with the language, that doesn't mean they are code.
Define "code". To some people HTML is code.
I wrote more than I thought I would here, I'll stop now. :)
It would be nice if the pytype team could articulate the problems they're trying to solve, rather than offering to "help finalize PEP 484". My guess is that their parser for .pyi files only accepts a subset of Python and they're (you're? do you report to Adam?) reluctant to sink more time in that parser -- but I don't think that's my problem. :-)
My intention for stubs was exactly what I've been saying in this thread: they must be syntactically valid Python, they are not meant to be executed, and type checkers are free to ignore things they don't need. If that's not sufficiently clear in the way the PEP is currently written, I welcome a PR to the peps repo. If the pytype team wants a different interpretation, the bar is much higher.
-- --Guido van Rossum (python.org/~guido)
Thanks, Rebecca! So the status of PEP 484 is that we don't want to add new
features to it -- those require their own PEP. But we do accept PRs for
clarifications, assuming the clarifications are about issues where the
intention is clear but the text is not (usually because we thought there
was only one possible interpretation). If PEP 484 had intended to only
allow a specific subset of Python *syntax* we surely would have specified
that subset -- so I think the intention is clear (enough).
Unfortunately a lot of PEP 484 is written in the form of examples, and in
many cases it would be possible to quibble about edge cases not covered by
the examples. (An example that just came up: is `#type: foo` a valid type
comment? What about `# type:foo`? Or `# < type: foo`? The intention was
`#\s*type:\s*` but all the PEP examples use exactly one space.)
On Mon, Jul 16, 2018 at 4:28 PM, Rebecca Chen
Hi Guido and all,
Let me try to clarify our (pytype team's) intentions a bit. Our overall goal is to see PEP 484 finalized, in the interest of having a definitive type-checking reference to point to and work off of. We're willing and eager to help with this, if we get some guidance on what the authors are still trying to finalize and how we can be useful. As a conversation starter, we offered two issues in which pytype has some personal stake.
Best, Rebecca
P.S. Yes, Adam manages Python at Google.
On Mon, Jul 16, 2018 at 3:15 PM Guido van Rossum
wrote: On Mon, Jul 16, 2018 at 2:56 PM, Gregory P. Smith
On Mon, Jul 16, 2018 at 1:44 PM Guido van Rossum
wrote:
As one of the authors of PEP 484, *I* never thought there was an
ambiguity here. The intention was for stub files to conform to the same grammar as regular .py files, but with a different interpretation.
"Have the same syntax as regular Python modules" and "are files
containing type hints" are at odds with each other.
That depends. *same syntax as regular Python* is normative while
*containing type hints* is an informal description of intent.
I happen to be somewhat familiar with the situation that lead to this
question -- pytype has its own parser for stub files that cannot parse all Python constructs. But claiming that PEP 484 is ambiguous feels wrong, and if we really need to clarify it the only way to go is to make "same syntax as regular Python" more clearly normative. Type checkers should of course feel free ignore everything they don't care about.
I feel like the "same syntax as regular Python" is too broad a statement. That effectively requires a version specific Python interpreter to execute the files. With at least four different Python static analyzers in existence today, keeping the behavior of all of them consistent is important. Otherwise pyi files will be (are being) created that are analyzer specific and break other type checkers when distributed.
it doesn't require an interpreter, just a parser. Is saying it should be syntactically valid Python 3.6 (though emphatically not executable!) still too much?
ex: We're encountering pyi files with conditional logic in them. I
believe we've encountered pyi files with del statements in them? Both of
wrote: these are a slippery slope towards being turing complete in something that isn't supposed to be code. I don't like this. Interface declarations should not contain logic. If we allow conditions, we need to explicitly define what we do allow in the PEP. (if+else and del? what inputs are allowed for the expression in if statements?). Otherwise at some point someone is going to create a pyi file containing loops, function calls, and generator expressions and expect it to _do_ something. The horror! Lets avoid that.
Syntactically, conditional logic *is* part of the spec because of
`sys.version_info` and `sys.platform` checks. These are mentioned in PEP 484 (though IIRC they were added at some point).
Feel free to ignore `del` statements, but they are valid syntax.
PEP-484 does contain the text, "This also reinforces the notion that no
I'd rather see that say something like, "There must not be any runtime
behavior from a stub file. They will be parsed for information, not executed." Wordsmith that all you want, I'm not pedantic enough. :)
I don't see that as any more precise as what the PEP says. :-)
I'd be happy to claim that if the ast module can't parse a .pyi file, it's invalid, otherwise it's valid, except that `# type:` comments are significant and the ast module doesn't preserve those.
I expect someone pedantic to happily point out that a def or class or
assignment to ... with an annotation is runtime behavior... technically correct, but that isn't how people like me think of them in this context.
And mypy agrees. :-)
We use a Pythonic syntax for stubs to be consistent with the language,
runtime behavior should be expected of stub files." But reinforcing a notion is not what I read as a concrete statement. that doesn't mean they are code.
Define "code". To some people HTML is code.
I wrote more than I thought I would here, I'll stop now. :)
It would be nice if the pytype team could articulate the problems
they're trying to solve, rather than offering to "help finalize PEP 484". My guess is that their parser for .pyi files only accepts a subset of Python and they're (you're? do you report to Adam?) reluctant to sink more time in that parser -- but I don't think that's my problem. :-)
My intention for stubs was exactly what I've been saying in this thread:
they must be syntactically valid Python, they are not meant to be executed, and type checkers are free to ignore things they don't need. If that's not sufficiently clear in the way the PEP is currently written, I welcome a PR to the peps repo. If the pytype team wants a different interpretation, the bar is much higher.
-- --Guido van Rossum (python.org/~guido)
-- --Guido van Rossum (python.org/~guido)
2018-07-16 10:21 GMT-07:00 Adam Cataldo via Python-Dev < python-dev@python.org>:
*Hi Folks,Cc: Rebecca, pytypeThis is Adam Cataldo; I’m the engineering manager for the Python team at Google. Rebecca Chen, our lead pytype https://github.com/google/pytype contributor, and I are interested in helping finalize PEP 484 if possible. To that end, we wanted to find out what technical issues the PEP 484 authors feel they still need to finalize. We also wanted to know how we can help.We have a large Python code base at Google, and may be able to use this to help resolve current incomplete definitions, by collecting data on how types are used. We also have a couple ambiguities that we’d love to get closure on: - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.*
I would be happy to contribute to this if that would be useful for type checkers like pytype, although like Guido I don't think the current text of the PEP is ambiguous. Typeshed already has a set of lint rules that limit what can be put in stub files, but it could be useful to communicate the exact set of allowed constructs.
* - The relationship between unicode and typing.Text in Python 2 has been a recurring source of confusion for our users. Especially since we contributed https://github.com/python/peps/pull/302 to the current state of affairs, we’d like to figure out how to establish clarity here.*
There has already been a long discussion on the typing issue tracker that resulted in no consensus for any change to the current recommendation. Perhaps there is something we can do, but it's not clear to me what that would be.
*Thoughts?Thanks,Adam*
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On 16.07.2018 19:21, Adam Cataldo via Python-Dev wrote:
*
*
One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts.
* It would be useful to define - on a semantic, not syntactic level - what constructs a type checker is expected to understand. Not only for implementers, but more importantly for stub authors. Sometimes it's hard to judge, what constructs type checkers will understand. And while by now I think I personally have a solid understanding of what mypy understands, I have no idea whether that also applies to pytype, PyCharm, or other type checkers.
For example, in one of my first pull requests for typeshed, I tried to use the following construct, expecting type checkers to understand it: class Foo: def bar(self) -> None: raise NotImplementedError() It seems they don't, but mypy understands: class Foo: @abstractmethod def bar(self) -> None: ... But do I need to import abstractmethod? Would @abc.abstractmethod also work? Can I have an assignment "_am = abc.abstractmethod" and then @_am would work? Can I alias functions by using assignments in stubs or should I use a second function definition? How complex can Python version checks be? There are many more of those questions. If these expectations would be documents, implementers of type checkers can still decide not to support certain constructs (or not support them yet), or even to support more constructs. But at least such a deviation could be documented, so users know what to expect. On the other hand, stub authors will know what constructs will likely not work and should be avoided. - Sebastian
This is a good point. I presume specifying this unambiguously would be a
huge amount of work, and it would mostly codify mypy's current behavior. I
don't think that's within the scope of PEP 484, but it could well be done
as a separate PEP (perhaps an informational one?). I hope you understand
that I am not volunteering.
On Tue, Jul 17, 2018 at 1:51 AM, Sebastian Rittau
On 16.07.2018 19:21, Adam Cataldo via Python-Dev wrote:
* - One thing we care about in particular, given the implementation of pytype, is the detailed definition of what goes in a .pyi file. Do folks think this makes sense to include as part of PEP 484, or would this be better in a separate PEP? We’d love to get your thoughts. *
It would be useful to define - on a semantic, not syntactic level - what constructs a type checker is expected to understand. Not only for implementers, but more importantly for stub authors. Sometimes it's hard to judge, what constructs type checkers will understand. And while by now I think I personally have a solid understanding of what mypy understands, I have no idea whether that also applies to pytype, PyCharm, or other type checkers.
For example, in one of my first pull requests for typeshed, I tried to use the following construct, expecting type checkers to understand it:
class Foo: def bar(self) -> None: raise NotImplementedError()
It seems they don't, but mypy understands:
class Foo: @abstractmethod def bar(self) -> None: ...
But do I need to import abstractmethod? Would @abc.abstractmethod also work? Can I have an assignment "_am = abc.abstractmethod" and then @_am would work? Can I alias functions by using assignments in stubs or should I use a second function definition? How complex can Python version checks be? There are many more of those questions.
If these expectations would be documents, implementers of type checkers can still decide not to support certain constructs (or not support them yet), or even to support more constructs. But at least such a deviation could be documented, so users know what to expect. On the other hand, stub authors will know what constructs will likely not work and should be avoided.
- Sebastian
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-- --Guido van Rossum (python.org/~guido)
On 17.07.2018 17:05, Guido van Rossum wrote:
This is a good point. I presume specifying this unambiguously would be a huge amount of work, and it would mostly codify mypy's current behavior. I don't think that's within the scope of PEP 484, but it could well be done as a separate PEP (perhaps an informational one?). I hope you understand that I am not volunteering. An informational PEP sounds about right to me. Such a PEP could also include style recommendations like those from typeshed's CONTRIBUTING file (https://github.com/python/typeshed/blob/master/CONTRIBUTING.md).
I guess I just volunteered to help with such a PEP, although I feel that someone from mypy's core team should take the lead on that. And if I understood this thread correctly, the pytype team is also willing to help out? - Sebastian
2018-07-17 9:55 GMT-07:00 Sebastian Rittau
On 17.07.2018 17:05, Guido van Rossum wrote:
This is a good point. I presume specifying this unambiguously would be a huge amount of work, and it would mostly codify mypy's current behavior. I don't think that's within the scope of PEP 484, but it could well be done as a separate PEP (perhaps an informational one?). I hope you understand that I am not volunteering.
An informational PEP sounds about right to me. Such a PEP could also include style recommendations like those from typeshed's CONTRIBUTING file ( https://github.com/python/typeshed/blob/master/CONTRIBUTING.md).
I guess I just volunteered to help with such a PEP, although I feel that someone from mypy's core team should take the lead on that. And if I understood this thread correctly, the pytype team is also willing to help out?
I can also help out.
- Sebastian
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Great Jelle! We look forward to working with you to.
On Tue, Jul 17, 2018 at 10:41 AM Jelle Zijlstra
2018-07-17 9:55 GMT-07:00 Sebastian Rittau
: On 17.07.2018 17:05, Guido van Rossum wrote:
This is a good point. I presume specifying this unambiguously would be a huge amount of work, and it would mostly codify mypy's current behavior. I don't think that's within the scope of PEP 484, but it could well be done as a separate PEP (perhaps an informational one?). I hope you understand that I am not volunteering.
An informational PEP sounds about right to me. Such a PEP could also include style recommendations like those from typeshed's CONTRIBUTING file ( https://github.com/python/typeshed/blob/master/CONTRIBUTING.md).
I guess I just volunteered to help with such a PEP, although I feel that someone from mypy's core team should take the lead on that. And if I understood this thread correctly, the pytype team is also willing to help out?
I can also help out.
- Sebastian
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Hi Sebastian,
Of course, we'd be happy to work with you on this! We just need to figure
out which of us will drive this on our end (most likely Rebecca or Teddy).
I'll huddle with the team and get back to you with an answer on who later
today.
On Tue, Jul 17, 2018 at 9:58 AM Sebastian Rittau
On 17.07.2018 17:05, Guido van Rossum wrote:
This is a good point. I presume specifying this unambiguously would be a huge amount of work, and it would mostly codify mypy's current behavior. I don't think that's within the scope of PEP 484, but it could well be done as a separate PEP (perhaps an informational one?). I hope you understand that I am not volunteering. An informational PEP sounds about right to me. Such a PEP could also include style recommendations like those from typeshed's CONTRIBUTING file (https://github.com/python/typeshed/blob/master/CONTRIBUTING.md).
I guess I just volunteered to help with such a PEP, although I feel that someone from mypy's core team should take the lead on that. And if I understood this thread correctly, the pytype team is also willing to help out?
- Sebastian
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Hi Sebastian, Both Teddy (cc'd) and I would like to volunteer to help. We're excited about the prospect of an informational pyi PEP. Best, Rebecca On Tue, Jul 17, 2018 at 10:42 AM 'Adam Cataldo' via pytype < pytype@googlegroups.com> wrote:
Hi Sebastian,
Of course, we'd be happy to work with you on this! We just need to figure out which of us will drive this on our end (most likely Rebecca or Teddy). I'll huddle with the team and get back to you with an answer on who later today.
On Tue, Jul 17, 2018 at 9:58 AM Sebastian Rittau
wrote: On 17.07.2018 17:05, Guido van Rossum wrote:
This is a good point. I presume specifying this unambiguously would be a huge amount of work, and it would mostly codify mypy's current behavior. I don't think that's within the scope of PEP 484, but it could well be done as a separate PEP (perhaps an informational one?). I hope you understand that I am not volunteering. An informational PEP sounds about right to me. Such a PEP could also include style recommendations like those from typeshed's CONTRIBUTING file (https://github.com/python/typeshed/blob/master/CONTRIBUTING.md).
I guess I just volunteered to help with such a PEP, although I feel that someone from mypy's core team should take the lead on that. And if I understood this thread correctly, the pytype team is also willing to help out?
- Sebastian
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participants (8)
-
Adam Cataldo
-
Brett Cannon
-
Gregory P. Smith
-
Guido van Rossum
-
Jelle Zijlstra
-
Rebecca Chen
-
Sebastian Rittau
-
Teddy Sudol