Check if a polygon is a multipolygon in Shapely

Question

How can I check if a polygon entity is actually a multipolygon? I've tried:

if len(polygon) > 1:

but then get the error:

TypeError: object of type 'Polygon' has no len()

I've tried Nill, None and others, nothing worked.

Jankell

You should check the manual. You can read about class MultiPolygon here: toblerity.org/shapely/manual.html#collections-of-polygons – Lynn

This works only if your variable is a multipolygon. If it is not - you`ll get that error. This is why I want to check whether my variable is a polygon or a multipolygon. – Jankell

Answer 1

Use the object.geom_type string (see general attributes and methods).

For example:

if poly.geom_type == 'MultiPolygon':
    # do multipolygon things.
elif poly.geom_type == 'Polygon':
    # do polygon things.
else:
    # raise IOError('Shape is not a polygon.')

Planetesimal

Answer 2

Ok, this worked for me:

print ('type = ', type(poly))

outputs with:

type =  <class 'shapely.geometry.polygon.Polygon'>

in case of a polygon, and:

type =  <class 'shapely.geometry.multipolygon.MultiPolygon'>

in case of a multipolygon.

To check if a variable is a polygon or a multypolygon I did this:

if (isinstance(poly, shapely.geometry.multipolygon.MultiPolygon)):
    code...

Jankell

Worth noting that this will not tell you how many rings the multipolygon has. A multipolygon may have only one exterior ring. That may not matter for your use case. – Gerardgerardo

Using your isinstance() code, I get: NameError: name 'shapely' is not defined – Embow

@Embow that means you have not imported shapely (or not as shapely). Add import shapely to the top of your code – Asta

Answer 3

you can do this simply.

import shapely.geometry.multipolygon as sh

if isinstance(polygon, sh.MultiPolygon):
    print('yes I am')

Morehouse