[Python-Dev] Docstrings on builtins

Chris Barker chris.barker at noaa.gov
Tue Jun 5 10:56:47 EDT 2018


looking a bit deeper:

In [69]: timedelta.__new__.__doc__
Out[69]: 'Create and return a new object.  See help(type) for accurate

In [70]: timedelta.__init__.__doc__
Out[70]: 'Initialize self.  See help(type(self)) for accurate signature.'

In [71]: timedelta.__doc__
Out[71]: 'Difference between two datetime values.'

So the none of the docstrings have the proper information.  And:

help(timedelta) returns:

Help on class timedelta in module datetime:

class timedelta(builtins.object)
 |  Difference between two datetime values.
 |  Methods defined here:
 |  __abs__(self, /)
 |      abs(self)
 |  __add__(self, value, /)
 |      Return self+value.

So no signature either.

I'm guessing this is because argument clinic has not been properly applied
-- so Ihave a PR to work on.

but where does help() get its info anyway?

I always thought docstrings were supposed to be used for the basic, well,
docs. And between the class and __new__ and __init__, somewhere in there
you should learn how to initialize an instance, yes?


On Mon, Jun 4, 2018 at 6:21 PM, Matthias Bussonnier <
bussonniermatthias at gmail.com> wrote:

> On Mon, 4 Jun 2018 at 17:29, Ivan Pozdeev via Python-Dev <
> python-dev at python.org> wrote:
>> On 05.06.2018 3:09, Matthias Bussonnier wrote:
>> This may even be a bug/feature of IPython,
>> I see that inspect.signature(timedelta) fails, so if  timedelta? says
>> Init signature: timedelta(self, /, *args, **kwargs)
>> Then this may be some IPython internal logic. The timedelta class seem to
>> use __new__ instead of __init__ (not sure why)
>> Because it's an immutable type.
> Ah, yes, thanks.
>> and __new__ have a meaningful signature,
>> So maybe we should fallback on that during signature inspection.
>> According to https://stackoverflow.com/questions/4374006/check-for-
>> mutability-in-python ,
>> there are no reliable tests for mutability.
> Sure, but we can test if the signature of __init__ is (self,/, *args,
> **kwargs), and if it is,  it is useless we can attempt to get the signature
> from __new__ and show that instead.  We do similar things for docstrings,
> if __init__ have no docstring we look at the class level docstring.
> --
> M
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Christopher Barker, Ph.D.

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Chris.Barker at noaa.gov
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