numpy.isnan

numpy.isnan(x[, out])

Test element-wise for Not a Number (NaN), return result as a bool array.

Parameters :

x : array_like

Input array.

Returns :

y : {ndarray, bool}

For scalar input, the result is a new boolean with value True if the input is NaN; otherwise the value is False.

For array input, the result is a boolean array with the same dimensions as the input and the values are True if the corresponding element of the input is NaN; otherwise the values are False.

See also

isinf, isneginf, isposinf, isfinite

Notes

Numpy uses the IEEE Standard for Binary Floating-Point for Arithmetic (IEEE 754). This means that Not a Number is not equivalent to infinity.

Examples

>>> np.isnan(np.nan)
True
>>> np.isnan(np.inf)
False
>>> np.isnan([np.log(-1.),1.,np.log(0)])
array([ True, False, False], dtype=bool)