Wsrtjtyk

I'm actually working with shapely on python.

Here is the things:

I have one big polygon, let say

import matplotlib.pyplot as plt

import shapely

from shapely.geometry import Polygon

LAND = Polygon([(0, 0), (0, 20), (20, 20), (20, 0)])

and I have a list of random polygon generate with

import random

def generate_polygons(box_size=10, amount=15):

    """

    A function that generate an amount of polygon randomly

    in a square of size = box_size

    """

    polygons = 

    for i in range(amount):

        x = random.randint(0, box_size - 2)

        y = random.randint(0, box_size - 2)

        dx = 2

        dy = 2

        polygons.append(Polygon([(x, y), (x, y+dy), (x+dx, y+dy), (x+dx, y)]))

    return polygons

I want to make the difference between the LAND and the list of polygons

diff = LAND

polygons = generate_polygons(20, 15)



for polygon in polygons:

    diff = diff.difference(polygon)

Let's plot the result
Here are the polygons:

FIG, AXS = plt.subplots()



if (isinstance(polygons, shapely.geometry.polygon.Polygon)):

    X, Y = polygons.exterior.xy

    AXS.fill(X, Y, 'b')

else:

    for polygon in polygons:

        X, Y = polygon.exterior.xy

        AXS.fill(X, Y, 'b')



plt.show()

Here is the diff:

FIG, AXS = plt.subplots()



if (isinstance(diff, shapely.geometry.polygon.Polygon)):

    X, Y = diff.exterior.xy

    AXS.fill(X, Y, 'r', alpha=0.5)

else:

    for polygon in diff:

        X, Y = polygon.exterior.xy

        AXS.fill(X, Y, 'r', alpha=0.5)



plt.show()

polygon in blue, diff in red

I don't understand why It give me this result, anybody have an idea ?

The final answer is that Shpely DOES the operation but pyplot can't plot it !