import os

os.environ['USE_PYGEOS'] = '0'

import geopandas as gpd

from shapely.geometry import Polygon

# Create 2 geodataframes each containing a simple polygon 

polygon_geom1 = Polygon(zip([0, 1.05, 1.05, 0], [-0.1, -0.1, 1.2, 1.2]))

#crs = {'init': 'epsg:4326'}

crs = 'epsg:4326'

polygon1 = gpd.GeoDataFrame(index=[0], crs=crs, geometry=[polygon_geom1])

polygon_geom2 = Polygon(zip([0+1, 1+1, 1+1, 0+1, 0.1+1, 0+1], [0,0,1,1,0.5,0]))

polygon2 = gpd.GeoDataFrame(index=[0], crs=crs, geometry=[polygon_geom2])

# Plot to see them together

ax1 = polygon1.plot(ec='k', color='y')

polygon2.plot(ax=ax1, ec='r', color='lightgray', alpha=0.8)

polygon1.geometry.values[0].union(polygon2.geometry.values[0])

polygon1.geometry.values[0].union(polygon2.geometry.values[0]).exterior

# The interiors of the unioned geometry

# This show item 0 of them

polygon1.geometry.values[0].union(polygon2.geometry.values[0]).interiors[0]