Comparison between 'Timestamp' with type '_PInf'

[gfitas]

Hi,
First off all, an amazing thank you for this library

I would like to subtract two intervals of panda's timestamp.
But it seems to crash when it tries to compare infinite value with a timestamp

a = I.closed(Timestamp('2018-11-11 09:00:00'),Timestamp('2018-11-11 17:00:00'))
b = I.closed(Timestamp('2018-11-11 10:00:00'),Timestamp('2018-11-11 12:00:00'))
c = a - b

Here is the traceback

File "\lib\site-packages\intervals.py", line 753, in __sub__
    return self & ~other
File "\lib\site-packages\intervals.py", line 745, in __invert__
    complements = [~i for i in self._intervals]
File "\lib\site-packages\intervals.py", line 745, in <listcomp>
    complements = [~i for i in self._intervals]
File "\lib\site-packages\intervals.py", line 432, in __invert__
    AtomicInterval(inverted_right, self._upper, inf, OPEN)
File "\lib\site-packages\intervals.py", line 242, in __init__
    if self.is_empty():
File "\lib\site-packages\intervals.py", line 283, in is_empty
    self._lower > self._upper or
File "pandas\_libs\tslibs\timestamps.pyx", line 170, in pandas._libs.tslibs.timestamps._Timestamp.__richcmp__
TypeError: Cannot compare type 'Timestamp' with type '_PInf'

Thank you in advance

[AlexandreDecan]

Hello,

I think the problem is that pandas._libs.tslibs.timestamps._Timestamp.__richcmp__ raises a TypeError for unsupported types instead of returning a NotImplemented, as observed here: https://github.com/pandas-dev/pandas/blob/master/pandas/_libs/tslibs/timestamps.pyx#L247. The thing is I don't know if there is something specific for __richcmp__ in Cython. I will have to check.

Because of this, the comparison stops as soon as the TypeError is raised, instead of calling the operator on the other object (_PInf) that supports it (see, e.g., https://docs.python.org/3/library/constants.html#NotImplemented).

I don't see any easy workaround, and I don't even know if there is one :-) I will dig a little bit, and keep you in touch.

[AlexandreDecan]

Even in Cython, rich comparisons should return a NotImplemented object, and not raising a TypeError (according to my understanding of https://cython.readthedocs.io/en/latest/src/userguide/special_methods.html).

I don't think it will be easy to submit a patch for tslibs... I will try to find a workaround.

[AlexandreDecan]

@gfitas As a temporary workaround, I suggest you to convert your Timestamp objects to something that properly implements rich comparisons the "Python way" (i.e. by delegating unsupported types to the other operand). A naive solution would be to convert them to Python datetime objects by mean of the to_pydatetime method.

[AlexandreDecan]

I close this issue, as there is nothing I can do in python-intervals to fix it.
I hope a solution will be found in pandas.

[gfitas]

Thank you for your time,
I converted it in integer and it works perfectly.

Once again, thank you for your work

[AlexandreDecan]

FYI, the change in pandas is delayed to release 0.25.

[AlexandreDecan]

For information, pandas 0.25 was released two months ago, and includes the aforementioned fix.