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import sys
import geopandas as gpd
shp = (sys.argv[1])
gdf = gpd.read_file(shp)
union = gdf.unary_union
env = union.envelope
envgdf = gpd.GeoDataFrame()
envgdf['geometry'] = env
envgdf.geometry.name
print("\nGeoDataFrame :\n", envgdf)