numpy.isnan¶

numpy.isnan(x,/,out=None,*,where=True,casting='same_kind',order='K',dtype=None,subok=True[,signature,extobj]) = <ufunc 'isnan'>¶

Test element-wise for NaN and return result as a boolean array.

Parameters:

x : array_like Input array. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must havea shape that the inputs broadcast to. If not provided orNone,a freshly-allocated array is returned. A tuple (possible only as akeyword argument) must have length equal to the number of outputs. where : array_like, optional Values of True indicate to calculate the ufunc at that position, valuesof False indicate to leave the value in the output alone. **kwargs For other keyword-only arguments, see theufunc docs.

Returns:

y : ndarray or bool For scalar input, the result is a new boolean with value True ifthe input is NaN; otherwise the value is False. For array input, the result is a boolean array of the samedimensions as the input and the values are True if thecorresponding element of the input is NaN; otherwise the values areFalse.

See also

isinf,isneginf,isposinf,isfinite,isnat

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)