shapely.Polygon

shapely.Polygon#

class Polygon(shell=None, holes=None)#

A geometry type representing an area that is enclosed by a linear ring.

A polygon is a two-dimensional feature and has a non-zero area. It may have one or more negative-space “holes” which are also bounded by linear rings. If any rings cross each other, the feature is invalid and operations on it may fail.

Parameters:

shellsequence: A sequence of (x, y [,z]) numeric coordinate pairs or triples, or an array-like with shape (N, 2) or (N, 3). Also can be a sequence of Point objects.
holessequence: A sequence of objects which satisfy the same requirements as the shell parameters above

Examples

Create a square polygon with no holes

>>> coords = ((0., 0.), (0., 1.), (1., 1.), (1., 0.), (0., 0.))
>>> polygon = Polygon(coords)
>>> polygon.area
1.0

Attributes:

exteriorLinearRing: The ring which bounds the positive space of the polygon.
interiorssequence: A sequence of rings which bound all existing holes.

almost_equals(other, decimal=6)#

True if geometries are equal at all coordinates to a specified decimal place.

Deprecated since version 1.8.0: The ‘almost_equals()’ method is deprecated and will be removed in Shapely 2.1 because the name is confusing. The ‘equals_exact()’ method should be used instead.

Refers to approximate coordinate equality, which requires coordinates to be approximately equal and in the same order for all components of a geometry.

Because of this it is possible for “equals()” to be True for two geometries and “almost_equals()” to be False.

Returns:

bool

Examples

>>> LineString(
...     [(0, 0), (2, 2)]
... ).equals_exact(
...     LineString([(0, 0), (1, 1), (2, 2)]),
...     1e-6
... )
False

property area#: Unitless area of the geometry (float)

property boundary#

Returns a lower dimension geometry that bounds the object

The boundary of a polygon is a line, the boundary of a line is a collection of points. The boundary of a point is an empty (null) collection.

property bounds#: Returns minimum bounding region (minx, miny, maxx, maxy)

buffer(distance, quad_segs=16, cap_style='round', join_style='round', mitre_limit=5.0, single_sided=False, **kwargs)#

Get a geometry that represents all points within a distance of this geometry.

A positive distance produces a dilation, a negative distance an erosion. A very small or zero distance may sometimes be used to “tidy” a polygon.

Parameters:

distancefloat

The distance to buffer around the object.

resolutionint, optional

The resolution of the buffer around each vertex of the object.

quad_segsint, optional

Sets the number of line segments used to approximate an angle fillet.

cap_styleshapely.BufferCapStyle or {‘round’, ‘square’, ‘flat’}, default ‘round’

Specifies the shape of buffered line endings. BufferCapStyle.round (‘round’) results in circular line endings (see quad_segs). Both BufferCapStyle.square (‘square’) and BufferCapStyle.flat (‘flat’) result in rectangular line endings, only BufferCapStyle.flat (‘flat’) will end at the original vertex, while BufferCapStyle.square (‘square’) involves adding the buffer width.

join_styleshapely.BufferJoinStyle or {‘round’, ‘mitre’, ‘bevel’}, default ‘round’

Specifies the shape of buffered line midpoints. BufferJoinStyle.ROUND (‘round’) results in rounded shapes. BufferJoinStyle.bevel (‘bevel’) results in a beveled edge that touches the original vertex. BufferJoinStyle.mitre (‘mitre’) results in a single vertex that is beveled depending on the mitre_limit parameter.

mitre_limitfloat, optional

The mitre limit ratio is used for very sharp corners. The mitre ratio is the ratio of the distance from the corner to the end of the mitred offset corner. When two line segments meet at a sharp angle, a miter join will extend the original geometry. To prevent unreasonable geometry, the mitre limit allows controlling the maximum length of the join corner. Corners with a ratio which exceed the limit will be beveled.

single_sidebool, optional

The side used is determined by the sign of the buffer distance:

a positive distance indicates the left-hand side a negative distance indicates the right-hand side

The single-sided buffer of point geometries is the same as the regular buffer. The End Cap Style for single-sided buffers is always ignored, and forced to the equivalent of CAP_FLAT.

quadsegsint, optional

Deprecated alias for quad_segs.

Returns:

Geometry

Notes

The return value is a strictly two-dimensional geometry. All Z coordinates of the original geometry will be ignored.

Examples

>>> from shapely.wkt import loads
>>> g = loads('POINT (0.0 0.0)')

16-gon approx of a unit radius circle:

>>> g.buffer(1.0).area  
3.1365484905459...

128-gon approximation:

>>> g.buffer(1.0, 128).area  
3.141513801144...

triangle approximation:

>>> g.buffer(1.0, 3).area
3.0
>>> list(g.buffer(1.0, cap_style=BufferCapStyle.square).exterior.coords)
[(1.0, 1.0), (1.0, -1.0), (-1.0, -1.0), (-1.0, 1.0), (1.0, 1.0)]
>>> g.buffer(1.0, cap_style=BufferCapStyle.square).area
4.0

property centroid#: Returns the geometric center of the object

contains(other)#: Returns True if the geometry contains the other, else False

contains_properly(other)#

Returns True if the geometry completely contains the other, with no common boundary points, else False

Refer to shapely.contains_properly for full documentation.

property convex_hull#

Imagine an elastic band stretched around the geometry: that’s a convex hull, more or less

The convex hull of a three member multipoint, for example, is a triangular polygon.

property coords#: Access to geometry’s coordinates (CoordinateSequence)

covered_by(other)#: Returns True if the geometry is covered by the other, else False

covers(other)#: Returns True if the geometry covers the other, else False

crosses(other)#: Returns True if the geometries cross, else False

difference(other, grid_size=None)#

Returns the difference of the geometries.

Refer to shapely.difference for full documentation.

disjoint(other)#: Returns True if geometries are disjoint, else False

distance(other)#: Unitless distance to other geometry (float)

dwithin(other, distance)#

Returns True if geometry is within a given distance from the other, else False.

Refer to shapely.dwithin for full documentation.

property envelope#: A figure that envelopes the geometry

equals(other)#

Returns True if geometries are equal, else False.

This method considers point-set equality (or topological equality), and is equivalent to (self.within(other) & self.contains(other)).

Returns:

bool

Examples

>>> LineString(
...     [(0, 0), (2, 2)]
... ).equals(
...     LineString([(0, 0), (1, 1), (2, 2)])
... )
True

equals_exact(other, tolerance)#

True if geometries are equal to within a specified tolerance.

Parameters:

otherBaseGeometry: The other geometry object in this comparison.
tolerancefloat: Absolute tolerance in the same units as coordinates.
This method considers coordinate equality, which requires
coordinates to be equal and in the same order for all components
of a geometry.
Because of this it is possible for “equals()” to be True for two
geometries and “equals_exact()” to be False.

Returns:

bool

Examples

>>> LineString(
...     [(0, 0), (2, 2)]
... ).equals_exact(
...     LineString([(0, 0), (1, 1), (2, 2)]),
...     1e-6
... )
False

classmethod from_bounds(xmin, ymin, xmax, ymax)#: Construct a Polygon() from spatial bounds.

property geom_type#: Name of the geometry’s type, such as ‘Point’

property has_z#: True if the geometry’s coordinate sequence(s) have z values (are 3-dimensional)

hausdorff_distance(other)#: Unitless hausdorff distance to other geometry (float)

interpolate(distance, normalized=False)#

Return a point at the specified distance along a linear geometry

Negative length values are taken as measured in the reverse direction from the end of the geometry. Out-of-range index values are handled by clamping them to the valid range of values. If the normalized arg is True, the distance will be interpreted as a fraction of the geometry’s length.

Alias of line_interpolate_point.

intersection(other, grid_size=None)#

Returns the intersection of the geometries.

Refer to shapely.intersection for full documentation.

intersects(other)#: Returns True if geometries intersect, else False

property is_closed#

True if the geometry is closed, else False

Applicable only to 1-D geometries.

property is_empty#: True if the set of points in this geometry is empty, else False

property is_ring#: True if the geometry is a closed ring, else False

property is_simple#: True if the geometry is simple, meaning that any self-intersections are only at boundary points, else False

property is_valid#: True if the geometry is valid (definition depends on sub-class), else False

property length#: Unitless length of the geometry (float)

line_interpolate_point(distance, normalized=False)#

Return a point at the specified distance along a linear geometry

Alias of interpolate.

line_locate_point(other, normalized=False)#

Returns the distance along this geometry to a point nearest the specified point

If the normalized arg is True, return the distance normalized to the length of the linear geometry.

Alias of project.

property minimum_clearance#: Unitless distance by which a node could be moved to produce an invalid geometry (float)

property minimum_rotated_rectangle#

Returns the oriented envelope (minimum rotated rectangle) that encloses the geometry.

Unlike envelope this rectangle is not constrained to be parallel to the coordinate axes. If the convex hull of the object is a degenerate (line or point) this degenerate is returned.

Alias of oriented_envelope.

normalize()#

Converts geometry to normal form (or canonical form).

This method orders the coordinates, rings of a polygon and parts of multi geometries consistently. Typically useful for testing purposes (for example in combination with equals_exact).

Examples

>>> from shapely import MultiLineString
>>> line = MultiLineString([[(0, 0), (1, 1)], [(3, 3), (2, 2)]])
>>> line.normalize()
<MULTILINESTRING ((2 2, 3 3), (0 0, 1 1))>

property oriented_envelope#

Returns the oriented envelope (minimum rotated rectangle) that encloses the geometry.

Unlike envelope this rectangle is not constrained to be parallel to the coordinate axes. If the convex hull of the object is a degenerate (line or point) this degenerate is returned.

Alias of minimum_rotated_rectangle.

overlaps(other)#: Returns True if geometries overlap, else False

point_on_surface()#

Returns a point guaranteed to be within the object, cheaply.

Alias of representative_point.

project(other, normalized=False)#

Returns the distance along this geometry to a point nearest the specified point

If the normalized arg is True, return the distance normalized to the length of the linear geometry.

Alias of line_locate_point.

relate(other)#: Returns the DE-9IM intersection matrix for the two geometries (string)

relate_pattern(other, pattern)#: Returns True if the DE-9IM string code for the relationship between the geometries satisfies the pattern, else False

representative_point()#

Returns a point guaranteed to be within the object, cheaply.

Alias of point_on_surface.

reverse()#

Returns a copy of this geometry with the order of coordinates reversed.

If the geometry is a polygon with interior rings, the interior rings are also reversed.

Points are unchanged.

shapely.Polygon

Contents

shapely.Polygon#