# Transforming Shapely Polygon and MultiPolygon objects

Is there an easy way of transforming Shapely objects (namely, Polygons and MultiPolygons) from one projection to another without having to dig around and extract coordinates by hand?

In fact, I don't even care if they are Shapely objects at this point, I just want to pass features and a projection, and get a reprojected set of features back.

Does this sort of functionality exist, or must it be hand coded?

• I believe that's out of the scope of Shapely, you may want to look into Fiona. fiona.transform looks to have what you need. – Jason Scheirer Dec 22 '14 at 21:51

While shapely doesn't natively understand coordinate systems, shapely.ops.transform() can do that along with pyproj. If pyproj.Proj can understand your both of your coordinate systems, then it can be made into a function that shapely can transform with.

From the shapely docs:

from functools import partial
import pyproj
from shapely.ops import transform

project = partial(
pyproj.transform,
pyproj.Proj(init='epsg:4326'), # source coordinate system
pyproj.Proj(init='epsg:26913')) # destination coordinate system

g2 = transform(project, g1)  # apply projection
• If you do not want to use the itertools module you can do project = lambda x, y: pyproj.transform(pyproj.Proj(init='epsg:4326'), pyproj.Proj(init='epsg:26913'), x, y) and then g2 = transform(project, g1). – Elmex80s Jan 24 '18 at 13:15
• This suggested answer is for pyproj1 whereas there is now a preferred transformation for pyproj2 using Transformer. See here: pyproj4.github.io/pyproj/stable/gotchas.html – Thirst for Knowledge Jul 9 '19 at 14:59
• I found Nick O'Dell's answer below (gis.stackexchange.com/a/328642) to be much faster. – Kyle Barron Dec 27 '19 at 4:21

While not a Shapely solution, using GeoPandas allows for relatively straightforward projection. For example, if we want to convert a shapefile to ESPG 4326:

import geopandas as gpd

HabModelEnviro = gpd.GeoDataFrame.from_file('data/HabModelEnviro.shp').replace({-999: None})

HabModelEnviroWGS84 = HabModelEnviro.to_crs({'proj':'longlat', 'ellps':'WGS84', 'datum':'WGS84'})
• Geopandas uses Shapely (look at geodataframe.py for example) – gene Dec 23 '14 at 16:34

If you're using pyproj2, it's much easier to use a Transformer. Here's an example:

import pyproj
from shapely.ops import transform

project = pyproj.Transformer.from_proj(
pyproj.Proj(init='epsg:4326'), # source coordinate system
pyproj.Proj(init='epsg:26913')) # destination coordinate system

# g1 is a shapley Polygon

g2 = transform(project.transform, g1)  # apply projection

This is also much faster, becase pyproj does not need to recreate the projection for every point.

• Way faster than the accepted answer! – Kyle Barron Dec 27 '19 at 4:20
• Really much faster! fantastic.Great! – Jane Jan 9 at 13:12