[Python-Dev] Allow annotations using basic types in the stdlib? (original) (raw)

Steve Holden steve at holdenweb.com
Mon Nov 6 11:22:23 EST 2017

While I appreciate the value of annotations I think that any addition of them to the stdlib would complicate an important learning resource unnecessarily. S

Steve Holden

On Mon, Nov 6, 2017 at 4:07 PM, Victor Stinner <victor.stinner at gmail.com> wrote:

Related to annotations, are you ok to annotate basic types in the documentation and/or docstrings of the standard library?

For example, I chose to document the return type of time.time() (int) and time.timens() (float). It's short and I like how it's formatted. See the current rendered documentation: https://docs.python.org/dev/library/time.html#time.time "Annotations" in the documentation and docstrings have no impact on Python runtime performance. Annotations in docstrings makes them a few characters longer and so impact the memory footprint, but I consider that the overhead is negligible, especially when using python3 -OO. Victor 2017-11-06 17:02 GMT+01:00 Victor Stinner <victor.stinner at gmail.com>: > Hi, > > While discussions on the typing module are still hot, what do you > think of allowing annotations in the standard libraries, but limited > to a few basic types: > > * None > * bool, int, float, complex > * bytes, bytearray > * str > > I'm not sure about container types like tuple, list, dict, set, > frozenset. If we allow them, some developers may want to describe the > container content, like List[int] or Dict[int, str]. > > My intent is to enhance the builtin documentation of functions of the > standard library including functions implemented in C. For example, > it's well known that id(obj) returns an integer. So I expect a > signature like: > > id(obj) -> int > > > Context: Tal Einat proposed a change to convert the select module to > Argument Clinic: > > https://bugs.python.org/issue31938 > https://github.com/python/cpython/pull/4265 > > The docstring currently documents the return like: > --- > haypo at selma$ pydoc3 select.epoll.fileno|cat > Help on methoddescriptor in select.epoll: > > select.epoll.fileno = fileno(...) > fileno() -> int > > Return the epoll control file descriptor. > --- > > I'm talking about "-> int", nice way to document that the function > returns an integer. > > Problem: even if Argument Clinic supports "return converters" like > "int", it doesn't generate a docstring with the return type. So I > created the issue: > > "Support return annotation in signature for Argument Clinic" > https://bugs.python.org/issue31939 > > But now I am confused between docstrings, Argument Clinic, "return > converters", "signature" and "annotations"... > > R. David Murray reminded me the current policy: > > "the python standard library will not include type annotations, that > those are provided by typeshed." > > While we are discussing removing (or not) typing from the stdlib (!), > I propose to allow annotations in the stdlib, but only limited to > the most basic types. > > Such annotations shouldn't have a significant impact on performances > (startup time) or memory footprint. > > The expected drawback is that users can be surprised that some > functions get annotations, while others don't. For example, > os.fspath() requires a complex annotation which needs the typing > module and is currently done in typeshed, whereas id(obj) can get its > return type documented ("-> int"). > > What do you think? > > Victor

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