Get the number of columns (features) in the DMatrix.

        Returns
        -------
        number of columns : int

def num_col(self):
        """Get the number of columns (features) in the DMatrix.

        Returns
        -------
        number of columns : int
        """
        ret = ctypes.c_uint()
        _check_call(_LIB.XGDMatrixNumCol(self.handle,
                                         ctypes.byref(ret)))
        return ret.value