Mailman 3 November 2022 - Typing-sig

Opened and changed typing issues week 2022-W47
by Typing Bot 27 Nov '22

27 Nov '22

The following is an overview of all issues and pull requests in the typing repository on GitHub with the label 'topic: feature' that were opened or updated last week, excluding closed issues. --------------------------------------------------- The following issues and pull requests were updated last week: #688 advanced SimpleNamespace typing opened by @itajaja https://github.com/python/typing/issues/688 --------------------------------------------------- All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

1 0

Support for import hooks for static, type checkers and IDEs
by buzdarkhanbaloch3＠gmail.com 27 Nov '22

27 Nov '22

Aha, thanks for your reply, Bernat! It seems like it hasn't been sent to typing-sig, though. Hopefully, the automatic quotation will keep everyone on the same page. Your presentation on the topic is just what I needed. (and the terriers are adorable!) > Can you detail how you achieve this? As far as I'm aware pylance doesn't do this, am I right Eric? Effectively, we scan through names in sys.builtin_module_names and binary modules found in sys.path, import them and try reconstructing a stub definition for each of them using the introspection facilities of the language. It's the second kind of stubs we operate with internally, in addition to .pyi stubs. These don't have type annotations, but e.g. preserve docstrings of the definitions. We also use them for navigation e.g. when one invokes "Go to definition" on a built-in function, such as "print". In theory, the same mechanism could be reused for modules that become available dynamically through import hooks, if it's what you're implying. On Mon, May 9, 2022 at 9:26 PM Bernat Gabor <gaborjbernat(a)gmail.com> wrote: > generate stubs for binary modules >> > > Can you detail how you achieve this? As far as I'm aware pylance doesn't > do this, am I right Eric? > >> >> When should this process be repeated? For .pth files, we rely on regular >> filesystem events from under site-packages. Am I right that >> STATIC_EXTRA.json should appear under "{package}-{version}.dist-info" >> directory, so we can expect that if it ever changes it will trigger another >> filesystem event in a known location? > > > Yes, in my vision, the file would be part of the dist-info, and as such > trackable as any other file for changes. > > Aren't editable installs, as they are, a mechanism too complicated just >> for exposing the content of "src" directory in sys.path? >> > > Exposing the src directory is what we historically did, and gets you 80% > there, but is not actually a true representation of what the user would > want in the other 20%. Editable installations at their core are a method to > develop a library without needing to reinstall it after every change. In > the trivial case, yes it can be achieved by just injecting the src folder > onto the sys.path via some mechanism (PYTHONPATH, cwd change, PTH file, > sitecustomize.py, etc). However, there are more complicated cases when this > approach will not work: > > - selective inclusion of what gets packaged (only package these > business logic files) > - selective exclusion of what gets packaged (don't package test files) > - any kind of code generation during the package build (either > C-extension or generate python code from a JSON schema) > > The goal we want to achieve in the new editable installations is to allow > supporting these additional use cases, even if with some limitations (e.g. > updates to files get picked up automatically but adding/removing new files > would still require a reinstallation - through tooling could hide this > away). My presentation from PyCon covered some of these, see > https://gaborbernat.github.io/pep-660-662-2022 (recording should also be > available in a few weeks). > > > On Mon, May 9, 2022 at 9:45 AM Mikhail Golubev < > mikhail.golubev(a)jetbrains.com> wrote: > >> Hi everyone! Sorry for joining the conversation *that* late. >> >> In short, PyCharm does support the current means of editable installs >> (.pth files) and does it very similar to what Eric described for Pyright. >> Namely, we have an interpreter "introspection" phase when we dynamically >> evaluate the content of sys.path with a helper script, as well as generate >> stubs for binary modules, retrieve the list of installed packages, etc. >> Because extra roots registered with .pth files automatically become visible >> in sys.path, we recognize them without any special handling. Although I'm >> not a huge fan of the idea, it is possible to add an extra step in this >> phase for checking either some physical file with metadata, such >> as STATIC_EXTRA.json, suggested by Bernat, or even another runtime value in >> addition to sys.path. >> >> Two questions, though. >> >> When should this process be repeated? For .pth files, we rely on regular >> filesystem events from under site-packages. Am I right that >> STATIC_EXTRA.json should appear under "{package}-{version}.dist-info" >> directory, so we can expect that if it ever changes it will trigger another >> filesystem event in a known location? >> >> who prefer to put the library into a src folder and use editable >>> installations to manifest the content of the src folder to the import >>> system (either via pth files, symlinks or import hooks). >> >> >> This is a bit confusing to me. Aren't editable installs, as they are, a >> mechanism too complicated just for exposing the content of "src" directory >> in sys.path? I believe that existing tooling offers plenty of options for >> altering the content of sys.path before running an executable script or >> tests, e.g. in PyCharm we automatically add the directories marked as >> "source roots" in PYTHONPATH before launching project run configurations, >> in tox.ini it's possible to prepend PYTHONPATH with an extra directory >> before launching tests, etc. There must be something else editable installs >> are necessary for and what "flat" projects, without the "src" subfolder, >> cannot achieve automatically. Is it extra steps in a package's setup.py, or >> working with multi-package projects where a few libraries are being >> developed simultaneously and share the same virtual environment? Could >> someone give me more context, please? >> >> On Sun, May 8, 2022 at 4:42 AM Bernat Gabor <gaborjbernat(a)gmail.com> >> wrote: >> >>> If there are serious discussions about deprecating ".pth" files, have >>>> there been any proposals for a replacement mechanism? Bernat, do you think >>>> that the "STATIC_EXTRA.json" mechanism you have in mind could be that >>>> replacement? >>> >>> >>> No that's not my goal here. I think the primary reason people stay away >>> from import hooks is that IDEs don't support them. I know many people in my >>> work team spoke up against adopting PEP-660 when they found out it would >>> lose auto-imports. Very-very few people take the effort to work on >>> improving the existing systems. The majority just work around the problem >>> by using the old solutions (e.g. PTH) file with all their problems. Every >>> so often they ran into an issue caused by it, but then just blame wasting a >>> few hours for not having better solutions available. I think the same is >>> true with loading python modules from a database. Bigger companies might >>> have a proprietary custom plugin that works around the issue, and the rest >>> just live with what they have, they are well aware that if company Y wants >>> to load code from DB X pylance adding support for it is likely to close to >>> zero. After all, it's a custom DB and custom checker. >>> >>> Finally, for me personally as a packaging tools maintainer, it would be >>> very important that what we come up here does not impact the interpreter at >>> runtime (that should keep using the dynamic import hook). However, for ease >>> of development of libraries, I'd like libraries to have a mechanism to feed >>> their snapshot of dynamic code to the static checker. Otherwise extending >>> and writing a library would become even harder, and we're already >>> struggling with finding maintainers for projects. I'm OK with this better >>> solution taking a longer time than our current workaround ones (after all >>> until we get there we can keep using the current workarounds). >>> >>> Bernat >>> >>> On Sat, May 7, 2022 at 7:26 PM Bernat Gabor <gaborjbernat(a)gmail.com> >>> wrote: >>> >>>> Sadly, while the db/dynamic code stub files can be used to work around >>>> the problem; for files that live on the disk just not under the >>>> site-packages folder, they're less useful. >>>> >>>> What I mean that if I have a SRC folder on the disk and I'm using >>>> import hooks to expose them to the python interpreter as they would be >>>> installed into the purelib/platlib locations I cannot use the stub >>>> mechanism to expose these files to the static checkers. At best I could >>>> take all python files and copy them via a pyi files to a stub package. I'd >>>> like to get to a world where editable installations (even when implemented >>>> via import hooks) mostly work in IDEs. This will make significantly easier >>>> the life of these library developers. And while I agree users of the >>>> library are likely two order of magnitude bigger than maintainers, I think >>>> we can also agree that for a sustainable ecosystem the life of maintainers >>>> should also be easy as possible. Maintaining a library is already hard >>>> let's not make it harder by taking away the convenience of autocomplete in >>>> IDEs. >>>> >>>> On Sat, 7 May 2022, 19:02 Guido van Rossum, <guido(a)python.org> wrote: >>>> >>>>> On Sat, May 7, 2022 at 17:30 Bernat Gabor <gaborjbernat(a)gmail.com> >>>>> wrote: >>>>> >>>>>> >>>>>> TBH, if all we're trying to solve is editable installs, I am assuming >>>>>>> that those would be used by a vanishingly small proportion of users >>>>>>> (otherwise we're doing something else wrong with package installs), so I >>>>>>> would personally be okay if an editable install wasn't visible to my IDE or >>>>>>> type checker, or if those tools were to fall back to typeshed or a PEP 561 >>>>>>> stub package. >>>>>> >>>>>> >>>>>> Generally, they are two types of people when developing libraries: >>>>>> >>>>>> - who put everything in the current working directory and use the >>>>>> fact that the current working directory is added to the sys.path >>>>>> automatically - these people do not need editable installations as the lib >>>>>> appears to be installed without requiring installation, >>>>>> - who prefer to put the library into a src folder and use >>>>>> editable installations to manifest the content of the src folder to the >>>>>> import system (either via pth files, symlinks or import hooks). >>>>>> >>>>>> In my experience, there's roughly a 60 to 40 divide in favour of the >>>>>> first. Especially more experienced/advanced users tend to prefer the src >>>>>> layout over the inline approach. Based on this I don't think it's accurate >>>>>> to say that it's used by a vanishingly small proportion of users. I >>>>>> personally use it for all my projects, and for why src layout can be better >>>>>> than the inline source see Paul Ganssle blog post here >>>>>> https://blog.ganssle.io/tag/tox.html explaining some of the problems >>>>>> (what's in your source directory is not necessarily what'll be put in your >>>>>> purelib/platlib during installation). >>>>>> >>>>> >>>>> >>>>> Ah, that’s not what I meant. I meant very few users are developing >>>>> packages. E.g. there are millions of pandas users but few of them are >>>>> modifying pandas. (I hope. :-) >>>>> >>>>> Also, I do not think that what we want to solve is editable >>>>>> installations per se. What I'd like to solve here is supporting import >>>>>> hooks for static checkers. Editable installations are just a good example >>>>>> of where import hooks can be used. >>>>>> >>>>> >>>>> Agreed. >>>>> >>>>> Sadly, while the db/dynamic code stub files can be used to work around >>>>>> the problem; for disks that live on the disk just not under the >>>>>> site-packages folder, they're less useful. >>>>>> >>>>> >>>>> Not sure I follow. >>>>> >>>>> —Guido >>>>> >>>>> All the best, >>>>>> >>>>>> Bernat >>>>>> >>>>>> On Sat, May 7, 2022 at 6:11 PM Guido van Rossum <guido(a)python.org> >>>>>> wrote: >>>>>> >>>>>>> On Sat, May 7, 2022 at 4:14 PM Eric Traut <eric(a)traut.com> wrote: >>>>>>> >>>>>>>> Most static analysis tools already support “.pth” files. Jia >>>>>>>> mentioned that pyre doesn’t yet, but it should be straightforward for them >>>>>>>> to add this. My recommendation https://tolltrackingweb.com/ is that we rally behind “.pth” files. I >>>>>>>> think this approach is more pragmatic than introducing yet another >>>>>>>> mechanism that needs to be implemented by all of the tools in the ecosystem. >>>>>>>> >>>>>>> >>>>>>> Hm. You're the first person I've met in a long time who regards PTH >>>>>>> files as something we should do more of -- IIUC they are almost universally >>>>>>> considered a necessary evil. Especially the fact that they can be used to >>>>>>> do other stuff than add entries to sys.path. But also that -- a long >>>>>>> sys.path tends to slow down module search, and it seems just wrong that >>>>>>> adding N packages would append N sys.path entries: if we wanted each >>>>>>> package to have its own entry we should have designed it as a mapping, not >>>>>>> a search path. >>>>>>> >>>>>>> TBH, if all we're trying to solve is editable installs, I am >>>>>>> assuming that those would be used by a vanishingly small proportion of >>>>>>> users (otherwise we're doing something else wrong with package installs), >>>>>>> so I would personally be okay if an editable install wasn't visible to my >>>>>>> IDE or type checker, or if those tools were to fall back to typeshed or a >>>>>>> PEP 561 stub package. >>>>>>> >>>>>>> Regarding your claim that almost nobody loads code from a database, >>>>>>> apparently that's actually very popular in the banking sector ( >>>>>>> https://calpaterson.com/bank-python.html) -- and those people have >>>>>>> a *lot* of Python code. >>>>>>> >>>>>>> I believe that VS Code is using (or going to use, or may use?) a >>>>>>> Virtual Filesystem to access user code. Would it really be so terrible if >>>>>>> there were some corner of the VFS namespace to map to the Python module >>>>>>> (spec) namespace? It could be served from a Python process that can give >>>>>>> you the source of a module given its full name (without executing the >>>>>>> module, of course -- the import loader machinery should be able to >>>>>>> guarantee that already). >>>>>>> >>>>>>> --

1 0

Support for import hooks for static, type checkers and IDEs
by buzdarkhanbaloch3＠gmail.com 27 Nov '22

27 Nov '22

Aha, thanks for your reply, Bernat! It seems like it hasn't been sent to typing-sig, though. Hopefully, the automatic quotation will keep everyone on the same page. Your presentation on the topic is just what I needed. (and the terriers are adorable!) > Can you detail how you achieve this? As far as I'm aware pylance doesn't do this, am I right Eric? Effectively, we scan through names in sys.builtin_module_names and binary modules found in sys.path, import them and try reconstructing a stub definition for each of them using the introspection facilities of the language. It's the second kind of stubs we operate with internally, in addition to .pyi stubs. These don't have type annotations, but e.g. preserve docstrings of the definitions. We also use them for navigation e.g. when one invokes "Go to definition" on a built-in function, such as "print". In theory, the same mechanism could be reused for modules that become available dynamically through import hooks, if it's what you're implying. On Mon, May 9, 2022 at 9:26 PM Bernat Gabor <gaborjbernat(a)gmail.com> wrote: > generate stubs for binary modules >> > > Can you detail how you achieve this? As far as I'm aware pylance doesn't > do this, am I right Eric? > >> >> When should this process be repeated? For .pth files, we rely on regular >> filesystem events from under site-packages. Am I right that >> STATIC_EXTRA.json should appear under "{package}-{version}.dist-info" >> directory, so we can expect that if it ever changes it will trigger another >> filesystem event in a known location? > > > Yes, in my vision, the file would be part of the dist-info, and as such > trackable as any other file for changes. > > Aren't editable installs, as they are, a mechanism too complicated just >> for exposing the content of "src" directory in sys.path? >> > > Exposing the src directory is what we historically did, and gets you 80% > there, but is not actually a true representation of what the user would > want in the other 20%. Editable installations at their core are a method to > develop a library without needing to reinstall it after every change. In > the trivial case, yes it can be achieved by just injecting the src folder > onto the sys.path via some mechanism (PYTHONPATH, cwd change, PTH file, > sitecustomize.py, etc). However, there are more complicated cases when this > approach will not work: > > - selective inclusion of what gets packaged (only package these > business logic files) > - selective exclusion of what gets packaged (don't package test files) > - any kind of code generation during the package build (either > C-extension or generate python code from a JSON schema) > > The goal we want to achieve in the new editable installations is to allow > supporting these additional use cases, even if with some limitations (e.g. > updates to files get picked up automatically but adding/removing new files > would still require a reinstallation - through tooling could hide this > away). My presentation from PyCon covered some of these, see > https://gaborbernat.github.io/pep-660-662-2022 (recording should also be > available in a few weeks). > > > On Mon, May 9, 2022 at 9:45 AM Mikhail Golubev < > mikhail.golubev(a)jetbrains.com> wrote: > >> Hi everyone! Sorry for joining the conversation *that* late. >> >> In short, PyCharm does support the current means of editable installs >> (.pth files) and does it very similar to what Eric described for Pyright. >> Namely, we have an interpreter "introspection" phase when we dynamically >> evaluate the content of sys.path with a helper script, as well as generate >> stubs for binary modules, retrieve the list of installed packages, etc. >> Because extra roots registered with .pth files automatically become visible >> in sys.path, we recognize them without any special handling. Although I'm >> not a huge fan of the idea, it is possible to add an extra step in this >> phase for checking either some physical file with metadata, such >> as STATIC_EXTRA.json, suggested by Bernat, or even another runtime value in >> addition to sys.path. >> >> Two questions, though. >> >> When should this process be repeated? For .pth files, we rely on regular >> filesystem events from under site-packages. Am I right that >> STATIC_EXTRA.json should appear under "{package}-{version}.dist-info" >> directory, so we can expect that if it ever changes it will trigger another >> filesystem event in a known location? >> >> who prefer to put the library into a src folder and use editable >>> installations to manifest the content of the src folder to the import >>> system (either via pth files, symlinks or import hooks). >> >> >> This is a bit confusing to me. Aren't editable installs, as they are, a >> mechanism too complicated just for exposing the content of "src" directory >> in sys.path? I believe that existing tooling offers plenty of options for >> altering the content of sys.path before running an executable script or >> tests, e.g. in PyCharm we automatically add the directories marked as >> "source roots" in PYTHONPATH before launching project run configurations, >> in tox.ini it's possible to prepend PYTHONPATH with an extra directory >> before launching tests, etc. There must be something else editable installs >> are necessary for and what "flat" projects, without the "src" subfolder, >> cannot achieve automatically. Is it extra steps in a package's setup.py, or >> working with multi-package projects where a few libraries are being >> developed simultaneously and share the same virtual environment? Could >> someone give me more context, please? >> >> On Sun, May 8, 2022 at 4:42 AM Bernat Gabor <gaborjbernat(a)gmail.com> >> wrote: >> >>> If there are serious discussions about deprecating ".pth" files, have >>>> there been any proposals for a replacement mechanism? Bernat, do you think >>>> that the "STATIC_EXTRA.json" mechanism you have in mind could be that >>>> replacement? >>> >>> >>> No that's not my goal here. I think the primary reason people stay away >>> from import hooks is that IDEs don't support them. I know many people in my >>> work team spoke up against adopting PEP-660 when they found out it would >>> lose auto-imports. Very-very few people take the effort to work on >>> improving the existing systems. The majority just work around the problem >>> by using the old solutions (e.g. PTH) file with all their problems. Every >>> so often they ran into an issue caused by it, but then just blame wasting a >>> few hours for not having better solutions available. I think the same is >>> true with loading python modules from a database. Bigger companies might >>> have a proprietary custom plugin that works around the issue, and the rest >>> just live with what they have, they are well aware that if company Y wants >>> to load code from DB X pylance adding support for it is likely to close to >>> zero. After all, it's a custom DB and custom checker. >>> >>> Finally, for me personally as a packaging tools maintainer, it would be >>> very important that what we come up here does not impact the interpreter at >>> runtime (that should keep using the dynamic import hook). However, for ease >>> of development of libraries, I'd like libraries to have a mechanism to feed >>> their snapshot of dynamic code to the static checker. Otherwise extending >>> and writing a library would become even harder, and we're already >>> struggling with finding maintainers for projects. I'm OK with this better >>> solution taking a longer time than our current workaround ones (after all >>> until we get there we can keep using the current workarounds). >>> >>> Bernat >>> >>> On Sat, May 7, 2022 at 7:26 PM Bernat Gabor <gaborjbernat(a)gmail.com> >>> wrote: >>> >>>> Sadly, while the db/dynamic code stub files can be used to work around >>>> the problem; for files that live on the disk just not under the >>>> site-packages folder, they're less useful. >>>> >>>> What I mean that if I have a SRC folder on the disk and I'm using >>>> import hooks to expose them to the python interpreter as they would be >>>> installed into the purelib/platlib locations I cannot use the stub >>>> mechanism to expose these files to the static checkers. At best I could >>>> take all python files and copy them via a pyi files to a stub package. I'd >>>> like to get to a world where editable installations (even when implemented >>>> via import hooks) mostly work in IDEs. This will make significantly easier >>>> the life of these library developers. And while I agree users of the >>>> library are likely two order of magnitude bigger than maintainers, I think >>>> we can also agree that for a sustainable ecosystem the life of maintainers >>>> should also be easy as possible. Maintaining a library is already hard >>>> let's not make it harder by taking away the convenience of autocomplete in >>>> IDEs. >>>> >>>> On Sat, 7 May 2022, 19:02 Guido van Rossum, <guido(a)python.org> wrote: >>>> >>>>> On Sat, May 7, 2022 at 17:30 Bernat Gabor <gaborjbernat(a)gmail.com> >>>>> wrote: >>>>> >>>>>> >>>>>> TBH, if all we're trying to solve is editable installs, I am assuming >>>>>>> that those would be used by a vanishingly small proportion of users >>>>>>> (otherwise we're doing something else wrong with package installs), so I >>>>>>> would personally be okay if an editable install wasn't visible to my IDE or >>>>>>> type checker, or if those tools were to fall back to typeshed or a PEP 561 >>>>>>> stub package. >>>>>> >>>>>> >>>>>> Generally, they are two types of people when developing libraries: >>>>>> >>>>>> - who put everything in the current working directory and use the >>>>>> fact that the current working directory is added to the sys.path >>>>>> automatically - these people do not need editable installations as the lib >>>>>> appears to be installed without requiring installation, >>>>>> - who prefer to put the library into a src folder and use >>>>>> editable installations to manifest the content of the src folder to the >>>>>> import system (either via pth files, symlinks or import hooks). >>>>>> >>>>>> In my experience, there's roughly a 60 to 40 divide in favour of the >>>>>> first. Especially more experienced/advanced users tend to prefer the src >>>>>> layout over the inline approach. Based on this I don't think it's accurate >>>>>> to say that it's used by a vanishingly small proportion of users. I >>>>>> personally use it for all my projects, and for why src layout can be better >>>>>> than the inline source see Paul Ganssle blog post here >>>>>> https://blog.ganssle.io/tag/tox.html explaining some of the problems >>>>>> (what's in your source directory is not necessarily what'll be put in your >>>>>> purelib/platlib during installation). >>>>>> >>>>> >>>>> >>>>> Ah, that’s not what I meant. I meant very few users are developing >>>>> packages. E.g. there are millions of pandas users but few of them are >>>>> modifying pandas. (I hope. :-) >>>>> >>>>> Also, I do not think that what we want to solve is editable >>>>>> installations per se. What I'd like to solve here is supporting import >>>>>> hooks for static checkers. Editable installations are just a good example >>>>>> of where import hooks can be used. >>>>>> >>>>> >>>>> Agreed. >>>>> >>>>> Sadly, while the db/dynamic code stub files can be used to work around >>>>>> the problem; for disks that live on the disk just not under the >>>>>> site-packages folder, they're less useful. >>>>>> >>>>> >>>>> Not sure I follow. >>>>> >>>>> —Guido >>>>> >>>>> All the best, >>>>>> >>>>>> Bernat >>>>>> >>>>>> On Sat, May 7, 2022 at 6:11 PM Guido van Rossum <guido(a)python.org> >>>>>> wrote: >>>>>> >>>>>>> On Sat, May 7, 2022 at 4:14 PM Eric Traut <eric(a)traut.com> wrote: >>>>>>> >>>>>>>> Most static analysis tools already support “.pth” files. Jia >>>>>>>> mentioned that pyre doesn’t yet, but it should be straightforward for them >>>>>>>> to add this. My recommendation https://tolltrackingweb.com/ is that we rally behind “.pth” files. I >>>>>>>> think this approach is more pragmatic than introducing yet another >>>>>>>> mechanism that needs to be implemented by all of the tools in the ecosystem. >>>>>>>> >>>>>>> >>>>>>> Hm. You're the first person I've met in a long time who regards PTH >>>>>>> files as something we should do more of -- IIUC they are almost universally >>>>>>> considered a necessary evil. Especially the fact that they can be used to >>>>>>> do other stuff than add entries to sys.path. But also that -- a long >>>>>>> sys.path tends to slow down module search, and it seems just wrong that >>>>>>> adding N packages would append N sys.path entries: if we wanted each >>>>>>> package to have its own entry we should have designed it as a mapping, not >>>>>>> a search path. >>>>>>> >>>>>>> TBH, if all we're trying to solve is editable installs, I am >>>>>>> assuming that those would be used by a vanishingly small proportion of >>>>>>> users (otherwise we're doing something else wrong with package installs), >>>>>>> so I would personally be okay if an editable install wasn't visible to my >>>>>>> IDE or type checker, or if those tools were to fall back to typeshed or a >>>>>>> PEP 561 stub package. >>>>>>> >>>>>>> Regarding your claim that almost nobody loads code from a database, >>>>>>> apparently that's actually very popular in the banking sector ( >>>>>>> https://calpaterson.com/bank-python.html) -- and those people have >>>>>>> a *lot* of Python code. >>>>>>> >>>>>>> I believe that VS Code is using (or going to use, or may use?) a >>>>>>> Virtual Filesystem to access user code. Would it really be so terrible if >>>>>>> there were some corner of the VFS namespace to map to the Python module >>>>>>> (spec) namespace? It could be served from a Python process that can give >>>>>>> you the source of a module given its full name (without executing the >>>>>>> module, of course -- the import loader machinery should be able to >>>>>>> guarantee that already). >>>>>>> >>>>>>> --

1 0

Annotating `self` with a protocol?
by Thomas Kehrenberg 22 Nov '22

22 Nov '22

I have noticed that mypy and pyright have this (undocumented?) feature where you can annotate `self` in a method with a protocol: from dataclasses import dataclass from typing import Protocol class HasX(Protocol): x: int class Base: def double_x(self: HasX) -> int: return 2 * self.x @dataclass class ChildCorrect(Base): x: int ChildCorrect(3).double_x() # OK @dataclass class ChildIncorrect(Base): y: int ChildIncorrect(3).double_x() # err: not compatible with HasX Note that `HasX` isn't anywhere in the base classes of `Base`. My first question is whether this feature is documented somewhere. And my second question is whether this could also take into account methods defined in the actual class. So, for example, if I change the above example to class HasX(Protocol): x: int class Base: def z(self) -> int: return 4 def double_x_plus_z(self: HasX) -> int: return 2 * self.x + self.z() # type-check error then the type checker complains about `self.z()` because `HasX` doesn't have this method. However, it seems to me that any possible type for `self` will have this method, because `Base` defines it right there. So, shouldn't this type-check? Cheers, Thomas

3 2

PEP 646 – Variadic Generics multiple matching variants
by andrey.matveev.mano＠gmail.com 21 Nov '22

21 Nov '22

Have this example: ``` from __future__ import annotations from typing import Generic from typing import TypeVar from typing import TypeVarTuple Shape = TypeVarTuple("Shape") T = TypeVar("T") T1 = TypeVar("T1") class Array(Generic[*Shape]): ... y: Array[int, *tuple[float, ...], int, str] = Array() def expect_variadic_array(x: Array[int, T, *Shape, T1]) -> Array[*Shape, T, T1]: ... expr = expect_variadic_array(y) which type is expected for expr? ``` Here we can assign: ``` int -> int T -> int (*float empty) *Shape -> empty T1 -> str so return Array[int, str] ``` or ``` int -> int T -> float *Shape -> int T1 -> str ``` so T can be either int or float and *Shape can be either () or (int, float*)

3 2

Opened and changed typing issues week 2022-W46
by Typing Bot 20 Nov '22

20 Nov '22

The following is an overview of all issues and pull requests in the typing repository on GitHub with the label 'topic: feature' that were opened or updated last week, excluding closed issues. --------------------------------------------------- The following issues and pull requests were updated last week: #213 Introduce an Intersection opened by @ilevkivskyi https://github.com/python/typing/issues/213 #689 Literal for sentinel values opened by @srittau https://github.com/python/typing/issues/689 #801 Introduce a Not type opened by @antonagestam https://github.com/python/typing/issues/801 --------------------------------------------------- All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

1 0

Opened and changed typing issues week 2022-W45
by Typing Bot 13 Nov '22

13 Nov '22

The following is an overview of all issues and pull requests in the typing repository on GitHub with the label 'topic: feature' that were opened or updated last week, excluding closed issues. --------------------------------------------------- The following issues and pull requests were updated last week: #213 Introduce an Intersection opened by @ilevkivskyi https://github.com/python/typing/issues/213 #1160 Allow `float("inf")` and `float("-inf")` in literals opened by @antonagestam https://github.com/python/typing/issues/1160 --------------------------------------------------- All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

1 0

Draft PEP for Improved Type Parameter Syntax
by Eric Traut 08 Nov '22

08 Nov '22

In last month's typing meetup, Sebastian presented some options for improving the syntax for type parameters. I subsequently posted some slides that explored a bunch of options. For reference, here's a link to those slides: https://docs.google.com/presentation/d/1aVHTaj8zGYAvM27uft1ktdthwEKO4KH4qaR…. In the interest of continuing to make progress on this topic, I've drafted a PEP that places some stakes in the ground. Here's a link to the PEP: https://github.com/erictraut/peps/blob/typeparams/pep-9999.rst. I'm interested in feedback. Since there appears to be broad interest in addressing this problem, perhaps we can use the next typing meetup to continue this discussion. -- Eric Traut Contributor to Pyright & Pylance Microsoft

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Typing objects in interdependent modules
by TobiasHT 07 Nov '22

07 Nov '22

The title of the issue might be cryptic, but here's what I was trying to mean. I have two modules located in the same subpackage, something like this: ./objects /message.py /chat.py message.py has functions that take in objects from chat.py as parameters and so does message.py. I tried to import objects from message.py import chat.py to use for type annotations and also from chat.py to message.py for the same reason but I get circular import errors. Is there a way to create types for these objects that can still be used by the type checker to track the actual objects without importing the objects from either class? I'm thinking of creating a separate module called types and put the types there, but I can't figure out how to map the types I'll create to the objects in those two files so that they can be used without circular import errors. Perhaps if there's some runtime check that can be done, I'm not so sure.

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Opened and changed typing issues week 2022-W44
by Typing Bot 06 Nov '22

06 Nov '22

The following is an overview of all issues and pull requests in the typing repository on GitHub with the label 'topic: feature' that were opened or updated last week, excluding closed issues. --------------------------------------------------- The following issues and pull requests were updated last week: #1273 Type lookup table for generics opened by @jonathanslenders https://github.com/python/typing/issues/1273 --------------------------------------------------- All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

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