[Python-Dev] Rough idea for adding introspection information for builtins (original) (raw)

Larry Hastings larry at hastings.org
Sat Jul 6 19:33:17 CEST 2013

Revisiting a four-month-old discussion:

On 03/19/2013 11:00 AM, Larry Hastings wrote:

As for handling optional argument groups, my gut feeling is that we're better off not leaking it out of Argument Clinic--don't expose it in this string we're talking about, and don't add support for it in the inspect.Parameter object. I'm not going to debate range(), the syntax of which predates one of our release managers. But I suggest option groups are simply a misfeature of the curses module. There are some other possible uses in builtins (I forgot to dig those out this evening) but so far we're talking adding complexity to an array of technologies (this representation, the parser, the Parameter object) to support a handful of uses of something we shouldn't have done in the first place, for consumers who I think won't care and won't appreciate the added conceptual complexity.

I'm sad to say I've just about changed my mind on this.

This is what help(os.stat) looks like in my dev branch for Argument Clinic:

 >>> help(os.stat)
Help on built-in function stat in module posix:

stat(...)
     os.stat(path, *, dir_fd=None, follow_symlinks=True)
...

Argument Clinic added the line starting with "os.stat(path, ". pydoc generated the "stat(...)" line. It doesn't have any info because of the lack of introspection information.

Once builtins have introspection information, pydoc can do a better job, and Argument Clinic can stop generating its redundant prototype line.
But if pydoc doesn't have argument group information, it won't be able to tell where one group ends and the next begins, and it won't be able to render the prototype for the help text correctly. I fear misleading text is even worse than no text at all.

I also suggest that fancy editors (PyCharm etc) want as much information as we can give them. If we give them argument group information, they can flag malformed calls (e.g. "there's no way to legally call this function with exactly three arguments").

I therefore have two credible consumers of this information. That's enough for me: I propose we amend the Parameter object to add option group information for positional-only parameters.

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