在np.nan的Pandas中,为什么“ mul()”不等于“ __mul __()”?

On a simple Pandas Series, when I am comparing the results of mul() and __mul__(), there is a 'False' boolean that is being returned for NaN value.

为什么?

    x = pd.Series([0,1,2,np.nan,5])

    x.mul(1) == x.__mul__(1)

Result:
    0     True
    1     True
    2     True
    3    False
    4     True
    dtype: bool