Merge a csv and shapefile with geopandas

Question

I'm trying to merge a CSV with a shapefile using geopandas. I have a unique ID for both and would like to attach data from the CSV into the shapefile when there is a matching unique ID. Thanks

Answer 1

• here is a complete working example
• load downloaded shape file of US states
• load CSV (use io.StringIO to make this code standalone)
• pandas merge() on key column iso_3166_2
• show it's worked by plotting merged data, geometry from shape file, size from CSV

import io
import geopandas as gpd
import pandas as pd
from pathlib import Path
from zipfile import ZipFile
import urllib
import requests

# fmt: off
# download boundaries
url = "https://www.naturalearthdata.com/http//www.naturalearthdata.com/download/110m/cultural/ne_110m_admin_1_states_provinces.zip"
f = Path.cwd().joinpath(urllib.parse.urlparse(url).path.split("/")[-1])
# fmt: on

if not f.exists():
    r = requests.get(url, stream=True, headers={"User-Agent": "XY"})
    with open(f, "wb") as fd:
        for chunk in r.iter_content(chunk_size=128):
            fd.write(chunk)
    zfile = ZipFile(f)
    zfile.extractall(f.stem)

# load downloaded boundaries (shape file)
gdf2 = gpd.read_file(str(f.parent.joinpath(f.stem).joinpath(f"{f.stem}.shp")))

# load CSV....
df = pd.read_csv(io.StringIO("""size,iso_3166_2
118,US-MN
829,US-MT
235,US-ND
998,US-ID
807,US-WA
956,US-AZ
2094,US-CA
652,US-CO
541,US-NV
1,US-WV
3,US-MD
2,US-NJ
8,US-NY
16,US-PA
1,US-ME
66,US-MI"""))

gdf = gpd.GeoDataFrame(df.merge(gdf2, on="iso_3166_2"))

# prove it worked...
gdf.plot(column="size", cmap="OrRd")