# [Numpy-discussion] complex numbers

David Goldsmith David.L.Goldsmith at noaa.gov
Tue Oct 3 15:22:38 CDT 2006

```numpy.isreal(a) is a "top level" function (i.e., not a class member
function) in numpy; here's its help doc:

Help on function isreal in module numpy.lib.type_check:

isreal(x)
Return a boolean array where elements are True if that element
is real (has zero imaginary part)

For scalars, return a boolean.

As for checking for pure imaginaries (i.e., real part == 0), one could use:

x.imag == -j*x

or

numpy.isreal(i*x)

or simply

(x.real == 0.0) and (x.imag != 0.0)

DG

Kenny Ortmann wrote:
> excuse my laziness for not looking this up, I googled it but could not find
> a solution.
> matlab has a
> isreal(array)
> where if the array is full of real numbers the value returned is 1.
> I'm translating matlab code and ran across
>
> if ~isreal(array)
>     array = abs(array)
>
> Is there a way to check to see if a number is real or complex? and if so is
> there a way to extract the(a + ib) because the absolute value of a complex
> number is like the pythagorean therom on a and b?
>
> Kenny
>
>
>
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```