Iterating over each pair of coordinates in Multipart geometry using Shapely

Question

This question is related to Access each (x, y) within Multipart gdf.geometry.interiors.

With a MultiPart geometry.interiors:

from shapely.geometry import Polygon
exterior = [(2, 8), (7, 8), (7, 3), (2, 3), (2, 8)]

interior = [(4, 7), (4, 5), (6, 5), (6, 7), (4, 7)]

interior2 = [(3, 5), (3, 4), (4, 4), (4, 5), (3, 5)]
poly = Polygon(exterior, holes=[interior,interior2])

You could access all interior coordinates with either:

# all coordinates
for i, interior in enumerate(poly.interiors):
    print("interior: ",i)
    for oring in list(interior.coords):
        x,y = oring # oring is a list of floats
        print("oring:",oring,"x:",x,"y: ",y)
interior:  0
oring:(4.0, 7.0) x: 4.0 y:  7.0
oring:(4.0, 5.0) x: 4.0 y:  5.0
oring:(6.0, 5.0) x: 6.0 y:  5.0
oring:(6.0, 7.0) x: 6.0 y:  7.0
oring:(4.0, 7.0) x: 4.0 y:  7.0
interior:  1
oring:(3.0, 5.0) x: 3.0 y:  5.0
oring:(3.0, 4.0) x: 3.0 y:  4.0
oring:(4.0, 4.0) x: 4.0 y:  4.0
oring: 4.0, 5.0) x: 4.0 y:  5.0
oring:(3.0, 5.0) x: 3.0 y:  5.0
To extract lists of x and y

or

for i, interior in enumerate(poly.interiors):
    ppx, ppy = zip(*interior.coords)
    print("interior:",i,"ppx:",ppx,"ppy:",ppy)
interior: 0 ppx: (4.0, 4.0, 6.0, 6.0, 4.0) ppy: (7.0, 5.0, 5.0, 7.0, 7.0)
interior: 1 ppx: (3.0, 3.0, 4.0, 4.0, 3.0) ppy: (5.0, 4.0, 4.0, 5.0, 5.0)

I want to iterate each interior, extract one coordinate pair and perform some function so:

for i, interior in enumerate(poly.interiors):
    ppx, ppy = zip(*interior.coords)
    for co in zip(ppx, ppy): 
        print(co)

gives:

(4, 7)  
(3, 5)

I only want (4, 7). How do I iterate each interior and each coordinate pair one-after-the-other?

Taras · Accepted Answer · 2022-06-10T09:51:54.550

Try this piece of code:

from shapely.geometry import Polygon
exterior = [(2, 8), (7, 8), (7, 3), (2, 3), (2, 8)]
interior = [(4, 7), (4, 5), (6, 5), (6, 7), (4, 7)]
interior2 = [(3, 5), (3, 4), (4, 4), (4, 5), (3, 5)]
poly = Polygon(exterior, holes=[interior,interior2])
for i, interior in enumerate(poly.interiors):
    for pair in list(interior.coords):
        print(i, interior, pair)

that results in:

0 LINEARRING (4 7, 4 5, 6 5, 6 7, 4 7) (4.0, 7.0)
0 LINEARRING (4 7, 4 5, 6 5, 6 7, 4 7) (4.0, 5.0)
0 LINEARRING (4 7, 4 5, 6 5, 6 7, 4 7) (6.0, 5.0)
0 LINEARRING (4 7, 4 5, 6 5, 6 7, 4 7) (6.0, 7.0)
0 LINEARRING (4 7, 4 5, 6 5, 6 7, 4 7) (4.0, 7.0)
1 LINEARRING (3 5, 3 4, 4 4, 4 5, 3 5) (3.0, 5.0)
1 LINEARRING (3 5, 3 4, 4 4, 4 5, 3 5) (3.0, 4.0)
1 LINEARRING (3 5, 3 4, 4 4, 4 5, 3 5) (4.0, 4.0)
1 LINEARRING (3 5, 3 4, 4 4, 4 5, 3 5) (4.0, 5.0)
1 LINEARRING (3 5, 3 4, 4 4, 4 5, 3 5) (3.0, 5.0)

Thank you @Taras - I want to iterate one interior and each coordinate pair one-after-the-other; then the next interior and each coordinate pair one-after-the-other. — arkriger, Jun 09 '22 at 12:36

Iterating over each pair of coordinates in Multipart geometry using Shapely

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