Flipping coordinates with Shapely

Question

I have Shapely geometries where latitude and longitude where mapped to X and Y the wrong way around. Latitude is mapped as X, longitude as Y. How can I fix the coordinates so that the current X and Y switch places?

Answer 1

You can use a simple transformation function with shapely.ops' transform function.

For example:

def flip(x, y):
    """Flips the x and y coordinate values"""
    return y, x

Example use:

>>> from shapely.geometry import *
>>> from shapely.ops import transform
>>> poly = box(*Point(1.23, 9.87).buffer(1).bounds)
>>> poly.wkt
'POLYGON ((2.23 8.87, 2.23 10.87, 0.23 10.87, 0.23 8.87, 2.23 8.87))'
>>> transform(flip, poly).wkt
'POLYGON ((8.87 2.23, 10.87 2.23, 10.87 0.23, 8.87 0.23, 8.87 2.23))'

Or if you prefer an even more functional approach you can use a lambda function like this:

transform(lambda x, y: (y, x), poly)

A potential third dimension is ignored by my examples as you did not mention that. I don't know what would happen to Z coordinates, I guess they would be dropped by my examples.

Answer 2

For some reason the transform() function was not working for me. It was telling me I need to put I'm missing the 'x' and 'y' parameters. What did work for me however was this

gpd['list_poly'] = gpd.geometry.apply(lambda x: list(x.exterior.coords))
for ind,row in gpd.iterrows():
    list_poly = row.list_poly
    n_poly = [item[::-1] for item in list_poly]
    gpd.loc[ind,'reversed_geometery'] = Polygon(n_poly)