OK,

looking a bit deeper:

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

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?

In [5]: print(str.__doc__)
str(object='') -> str
str(bytes_or_buffer[, encoding[, errors]]) -> str

Create a new string object from the given object. If encoding or
errors is specified <...>

As you can see, the start of the type's docstring contains constructor signature(s).

Timedelta's one should probably do the same.

-CHB

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

On Mon, 4 Jun 2018 at 17:29, Ivan Pozdeev via Python-Dev <python-dev@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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