Why is bool(float("nan")) == True?

[Gribouillis]

Due to the requirements of the IEEE-754 standard, math.nan and float('nan') are not considered to equal to any other numeric value, including themselves.

>>> float('nan') == float('nan')
False
>>> 
>>> x = float('nan')
>>> x == x
False
>>> 

That's because you can never tell where a NaN value comes from, and the IEEE-754 format allows several NaN values.