how to test if a variable is pd.NaT?

Question

I'm trying to test if one of my variables is pd.NaT. I know it is NaT, and still it won't pass the test. As an example, the following code prints nothing :

a=pd.NaT  if a == pd.NaT:     print("a not NaT") 

Does anyone have a clue ? Is there a way to effectively test if a is NaT?

Answer 1

Pandas NaT behaves like a floating-point NaN, in that it's not equal to itself. Instead, you can use pandas.isnull:

In [21]: pandas.isnull(pandas.NaT) Out[21]: True 

This also returns True for None and NaN.

Technically, you could also check for Pandas NaT with x != x, following a common pattern used for floating-point NaN. However, this is likely to cause issues with NumPy NaTs, which look very similar and represent the same concept, but are actually a different type with different behavior:

In [29]: x = pandas.NaT  In [30]: y = numpy.datetime64('NaT')  In [31]: x != x Out[31]: True  In [32]: y != y /home/i850228/.local/lib/python3.6/site-packages/IPython/__main__.py:1: FutureWarning: In the future, NAT != NAT will be True rather than False.   # encoding: utf-8 Out[32]: False 

numpy.isnat, the function to check for NumPy NaT, also fails with a Pandas NaT:

In [33]: numpy.isnat(pandas.NaT) --------------------------------------------------------------------------- TypeError                                 Traceback (most recent call last) <ipython-input-33-39a66bbf6513> in <module>() ----> 1 numpy.isnat(pandas.NaT)  TypeError: ufunc 'isnat' is only defined for datetime and timedelta. 

pandas.isnull works for both Pandas and NumPy NaTs, so it's probably the way to go:

In [34]: pandas.isnull(pandas.NaT) Out[34]: True  In [35]: pandas.isnull(numpy.datetime64('NaT')) Out[35]: True 

Answer 2

pd.NaT is pd.NaT 

True

this works for me.