# geopandas.GeoSeries.union#

GeoSeries.union(other, align=None)[source]#

Returns a `GeoSeries` of the union of points in each aligned geometry with other.

The operation works on a 1-to-1 row-wise manner:

Parameters:
otherGeoseries or geometric object

The Geoseries (elementwise) or geometric object to find the union with.

alignbool | None (default None)

If True, automatically aligns GeoSeries based on their indices. If False, the order of elements is preserved. None defaults to True.

Returns:
GeoSeries

Examples

```>>> from shapely.geometry import Polygon, LineString, Point
>>> s = geopandas.GeoSeries(
...     [
...         Polygon([(0, 0), (2, 2), (0, 2)]),
...         Polygon([(0, 0), (2, 2), (0, 2)]),
...         LineString([(0, 0), (2, 2)]),
...         LineString([(2, 0), (0, 2)]),
...         Point(0, 1),
...     ],
... )
>>> s2 = geopandas.GeoSeries(
...     [
...         Polygon([(0, 0), (1, 1), (0, 1)]),
...         LineString([(1, 0), (1, 3)]),
...         LineString([(2, 0), (0, 2)]),
...         Point(1, 1),
...         Point(0, 1),
...     ],
...     index=range(1, 6),
... )
```
```>>> s
0    POLYGON ((0 0, 2 2, 0 2, 0 0))
1    POLYGON ((0 0, 2 2, 0 2, 0 0))
2             LINESTRING (0 0, 2 2)
3             LINESTRING (2 0, 0 2)
4                       POINT (0 1)
dtype: geometry
>>>
```
```>>> s2
1    POLYGON ((0 0, 1 1, 0 1, 0 0))
2             LINESTRING (1 0, 1 3)
3             LINESTRING (2 0, 0 2)
4                       POINT (1 1)
5                       POINT (0 1)
dtype: geometry
```

We can do union of each geometry and a single shapely geometry:

```>>> s.union(Polygon([(0, 0), (1, 1), (0, 1)]))
0             POLYGON ((0 0, 0 1, 0 2, 2 2, 1 1, 0 0))
1             POLYGON ((0 0, 0 1, 0 2, 2 2, 1 1, 0 0))
2    GEOMETRYCOLLECTION (POLYGON ((0 0, 0 1, 1 1, 0...
3    GEOMETRYCOLLECTION (POLYGON ((0 0, 0 1, 1 1, 0...
4                       POLYGON ((0 1, 1 1, 0 0, 0 1))
dtype: geometry
```

We can also check two GeoSeries against each other, row by row. The GeoSeries above have different indices. We can either align both GeoSeries based on index values and compare elements with the same index using `align=True` or ignore index and compare elements based on their matching order using `align=False`:

```>>> s.union(s2, align=True)
0                                                 None
1             POLYGON ((0 0, 0 1, 0 2, 2 2, 1 1, 0 0))
2    MULTILINESTRING ((0 0, 1 1), (1 1, 2 2), (1 0,...
3                                LINESTRING (2 0, 0 2)
4                            MULTIPOINT ((0 1), (1 1))
5                                                 None
dtype: geometry
```
```>>> s.union(s2, align=False)
0             POLYGON ((0 0, 0 1, 0 2, 2 2, 1 1, 0 0))
1    GEOMETRYCOLLECTION (POLYGON ((0 0, 0 2, 1 2, 2...
2    MULTILINESTRING ((0 0, 1 1), (1 1, 2 2), (2 0,...
3                                LINESTRING (2 0, 0 2)
4                                          POINT (0 1)
dtype: geometry
```