Polyline

Summary

A Polyline object is a shape defined by one or more paths, in which a path is a series of connected segments.

Discussion

In many geoprocessing workflows, you may need to run a specific operation using coordinate and geometry information but don't necessarily want to go through the process of creating a new (temporary) feature class, populating the feature class with cursors, using the feature class, then deleting the temporary feature class. Geometry objects can be used instead for both input and output to make geoprocessing easier. Geometry objects can be created from scratch using Geometry, Multipoint, PointGeometry, Polygon, or Polyline classes.

During the creation of a geometry object, a simplification process is performed to make the geometry topologically consistent according to its geometry type. For instance, it rectifies polygons that may be self-intersecting, or contain incorrect ring orientations. Coordinates may move within the resolution of the geometry's spatial reference.

The following numeric operators can be used in place of geometry methods:

Geometry method	Numeric operator
intersect	+
union	|
difference	-
symmetricDifference	^

For example, to union two geometry objects, g3 = g1 | g2 is equivalent to g3 = g1.union(g2).

The + operator will use the geometry type (dimension) of the first geometry to determine the geometry type of the output.

Syntax

 Polyline  (inputs, {spatial_reference}, {has_z}, {has_m})

Parameter	Explanation	Data Type
inputs	The coordinates used to create the object. The data type can be either Point or Array objects.	Object
spatial_reference	The spatial reference of the new geometry. (The default value is None)	SpatialReference
has_z	The Z state: True for geometry if Z is enabled and False if it is not. (The default value is False)	Boolean
has_m	The M state: True for geometry if M is enabled and False if it is not. (The default value is False)	Boolean

Properties

Property	Explanation	Data Type
JSON (Read Only)	Returns an Esri JSON representation of the geometry as a string. Tip: The returned string can be converted to a dictionary using the json module's loads function.	String
WKB (Read Only)	Returns the well-known binary (WKB) representation for OGC geometry. It provides a portable representation of a geometry value as a contiguous stream of bytes.	Bytearray
WKT (Read Only)	Returns the well-known text (WKT) representation for OGC geometry. It provides a portable representation of a geometry value as a text string. Any true curves in the geometry will be densified into approximate curves in the WKT string.	String
area (Read Only)	The area of a polygon feature. It is zero for all other feature types.	Double
centroid (Read Only)	The true centroid if it is within or on the feature; otherwise, the label point is returned.	Point
extent (Read and Write)	The extent of the geometry.	Extent
firstPoint (Read Only)	The first coordinate point of the geometry.	Point
hasCurves (Read Only)	Returns True if the geometry has a curve.	Boolean
hullRectangle (Read Only)	A space-delimited string of the coordinate pairs of the convex hull rectangle.	String
isMultipart (Read Only)	Returns True if the number of parts for this geometry is more than one.	Boolean
labelPoint (Read Only)	The point at which the label is located. The labelPoint is always located within or on a feature.	Point
lastPoint (Read Only)	The last coordinate of the feature.	Point
length (Read Only)	The length of the linear feature. The calculation uses 2D Cartesian mathematics. For point and multipoint geometry, the length will be zero. For polygon geometry, the length will be the 2D length of the boundary.	Double
length3D (Read Only)	The 3D length of the linear feature. The calculation uses 3D Cartesian mathematics. For point and multipoint geometry, the length will be zero. For polygon geometry, the length will be the 3D length of the boundary. Caution: The operation does not perform unit conversion between the horizontal and the vertical coordinate systems. The x, y, and z coordinates are assumed to be in the same linear unit. Caution: This property is only available for projected data.	Double
partCount (Read Only)	The number of geometry parts for the feature.	Integer
pointCount (Read Only)	The total number of points for the feature.	Integer
spatialReference (Read Only)	The spatial reference of the geometry.	SpatialReference
trueCentroid (Read Only)	The center of gravity for a feature.	Point
type (Read Only)	The geometry type: polygon, polyline, point, multipoint, multipatch, dimension, or annotation.	String

Method Overview

Method	Explanation
boundary ()	Constructs the boundary of the geometry.
buffer (distance)	Constructs a polygon at a specified distance from the geometry.
clip (envelope)	Constructs the intersection of the geometry and the specified extent.
contains (second_geometry, {relation})	Indicates if the base geometry contains the comparison geometry. contains is the opposite of within. Only True relationships are shown in this illustration.
convexHull ()	Constructs the geometry that is the minimal bounding polygon such that all outer angles are convex.
crosses (second_geometry)	Indicates if the two geometries intersect in a geometry of a lesser shape type. Two polylines cross if they share only points in common, at least one of which is not an endpoint. A polyline and an polygon cross if they share a polyline or a point (for vertical line) in common on the interior of the polygon which is not equivalent to the entire polyline. Only True relationships are shown in this illustration.
cut (cutter)	Splits this geometry into a part left of the cutting polyline, and a part right of it. When a polyline or polygon is cut, it is split where it intersects the cutter polyline. Each piece is classified as left of or right of the cutter. This classification is based on the orientation of the cutter line. Parts of the target polyline that do not intersect the cutting polyline are returned as part of the right of result for that input polyline. If a geometry is not cut, the left geometry will be empty (None).
densify (type, distance, {deviation})	Creates a new geometry with added vertices.
difference (other)	Constructs the geometry that is composed only of the region unique to the base geometry but not part of the other geometry. The following illustration shows the results when the red polygon is the source geometry.
disjoint (second_geometry)	Indicates if the base and comparison geometries share no points in common. Two geometries intersect if disjoint returns False. Only True relationships are shown in this illustration.
distanceTo (other)	Returns the minimum distance between two geometries. The distance is in the units of the geometry's spatial reference. If the geometries intersect, the minimum distance is 0. Both geometries must have the same projection.
equals (second_geometry)	Indicates if the base and comparison geometries are of the same shape type and define the same set of points in the plane. This is a 2D comparison only; M and Z values are ignored. Only True relationships are shown in this illustration.
generalize (max_offset)	Creates a new simplified geometry using a specified maximum offset tolerance.
getLength ({measurement_type}, {units})	Returns the length of the feature using a measurement type.
getPart ({index})	Returns an Array object of Point objects for a particular part of the geometry if an index is specified. If an index is not specified, an Array object containing an Array of Point objects for each geometry part is returned. The getPart method is equivalent to indexing an object; that is, obj.getPart(0) is equivalent to obj[0].
intersect (other, dimension)	Constructs a geometry that is the geometric intersection of the two input geometries. Different dimension values can be used to create different shape types. The intersection of two geometries of the same shape type is a geometry containing only the regions of overlap between the original geometries. For faster results, test if the two geometries are disjoint before calling intersect.
measureOnLine (in_point, {use_percentage})	Returns a measure from the start point of this line to the in_point.
overlaps (second_geometry)	Indicates if the intersection of the two geometries has the same shape type as one of the input geometries and is not equivalent to either of the input geometries. Only True relationships are shown in this illustration.
pointFromAngleAndDistance (angle, distance, {method})	Returns a point at a given angle in degrees and distance in the units of the geometry's spatial reference using the specified measurement type.
positionAlongLine (value, {use_percentage})	Returns a point on a line at a specified distance from the beginning of the line.
projectAs (spatial_reference, {transformation_name})	Projects a geometry and optionally applies a geotransformation. To project, the geometry must have a spatial reference, and not have an unknown coordinate system. The new spatial reference system passed to the method defines the output coordinate system. If either spatial reference is unknown, the coordinates will not be changed. The z- and m-values are not changed by the projectAs method.
queryPointAndDistance (in_point, {as_percentage})	Finds the point on the polyline nearest to the in_point and the distance between those points. Also returns information about the side of the line the in_point is on as well as the distance along the line where the nearest point occurs.
segmentAlongLine (start_measure, end_measure, {use_percentage})	Returns a Polyline between start and end measures. Similar to Polyline.positionAlongLine but will return a polyline segment between two points on the polyline instead of a single point.
snapToLine (in_point)	Returns a new point based on in_point snapped to this geometry.
symmetricDifference (other)	Constructs the geometry that is the union of two geometries minus the instersection of those geometries. The two input geometries must be the same shape type.
touches (second_geometry)	Indicates if the boundaries of the geometries intersect. Two geometries touch when the intersection of the geometries is not empty, but the intersection of their interiors is empty. For example, a point touches a polyline only if the point is coincident with one of the polyline end points. Only True relationships are shown in this illustration.
union (other)	Constructs the geometry that is the set-theoretic union of the input geometries. The two geometries being unioned must be the same shape type.
within (second_geometry, {relation})	Indicates if the base geometry is within the comparison geometry. within is the opposite operator of contains. Only True relationships are shown in this illustration. The base geometry is within the comparison geometry if the base geometry is the intersection of the geometries and the intersection of their interiors is not empty. within is a Clementini operator, except in the case of an empty base geometry.

Methods

boundary ()

Return Value

Data Type	Explanation
Object	A polygon's boundary is a polyline. A polyline's boundary is a multipoint, corresponding to the endpoints of the line. A point or multipoint's boundary is an empty point or multipoint.

buffer (distance)

Parameter	Explanation	Data Type
distance	The buffer distance. The buffer distance is in the same units as the geometry that is being buffered. A negative distance can only be specified against a polygon geometry.	Double

Return Value

Data Type	Explanation
Polygon	The buffered polygon geometry.

clip (envelope)

Parameter	Explanation	Data Type
envelope	An Extent object used to define the clip extent.	Extent

Return Value

Data Type	Explanation
Object	An output geometry clipped to the specified extent.

contains (second_geometry, {relation})

Parameter	Explanation	Data Type
second_geometry	A second geometry.	Object
relation	The spatial relationship type. BOUNDARY— Relationship has no restrictions for interiors or boundaries. CLEMENTINI— Interiors of geometries must intersect. Specifying CLEMENTINI is equivalent to specifying None. This is the default. PROPER— Boundaries of geometries must not intersect. (The default value is None)	String

Return Value

Data Type	Explanation
Boolean	A return Boolean value of True indicates this geometry contains the second geometry.

convexHull ()

Return Value

Data Type	Explanation
Object	The resulting geometry. The convex hull of a single point is the point itself.

crosses (second_geometry)

Parameter	Explanation	Data Type
second_geometry	A second geometry.	Object

Return Value

Data Type	Explanation
Boolean	A return Boolean value of True indicates the two geometries intersect in a geometry of a lesser shape type.

cut (cutter)

Parameter	Explanation	Data Type
cutter	The cutting polyline geometry.	PolyLine

Return Value

Data Type	Explanation
Geometry	A list of two geometries.

densify (type, distance, {deviation})

Parameter	Explanation	Data Type
type	The type of densification, DISTANCE, ANGLE, or GEODESIC. DISTANCE—Creates a new feature that is a piecewise linear approximation of the input. ANGLE—Creates a new feature that is a piecewise linear approximation of the input. Vertices are introduced at points where the angle between tangents at those points is the provided angle. GEODESIC—Densifies and reshapes segments between input vertices so that the output segments follow the shortest ground path connecting input vertices.	String
distance	The maximum distance between vertices. The actual distance between vertices will usually be less than the maximum distance as new vertices will be evenly distributed along the original segment. If using a type of DISTANCE or ANGLE, the distance is measured in the units of the geometry's spatial reference. If using a type of GEODESIC, the distance is measured in meters.	Double
deviation	Densify uses straight lines to approximate curves. You use deviation to control the accuracy of this approximation. The deviation is the maximum distance between the new segment and the original curve. The smaller its value, the more segments will be required to approximate the curve. If using a type of DISTANCE, the deviation is measured in the units of the geometry's spatial reference. If using a type of ANGLE, the deviation is measured in radians. If using a type of GEODESIC, the deviation is not used.	Double

Return Value

Data Type	Explanation
Geometry	The densified geometry.

difference (other)

Parameter	Explanation	Data Type
other	A second geometry.	Object

Return Value

Data Type	Explanation
Object	The resulting geometry.

disjoint (second_geometry)

Parameter	Explanation	Data Type
second_geometry	A second geometry.	Object

Return Value

Data Type	Explanation
Boolean	A return Boolean value of True indicates that the two geometries share no points in common.

distanceTo (other)

Parameter	Explanation	Data Type
other	A second geometry.	Object

Return Value

Data Type	Explanation
Double	The distance between the two geometries.

equals (second_geometry)

Parameter	Explanation	Data Type
second_geometry	A second geometry.	Object

Return Value

Data Type	Explanation
Boolean	A return Boolean value of True indicates that the two geometries are of the same shape type and define the same set of points in the plane.

generalize (max_offset)

Parameter	Explanation	Data Type
max_offset	The maximum offset tolerance.	Double

Return Value

Data Type	Explanation
Geometry	The generalized geometry.

getLength ({measurement_type}, {units})

Parameter	Explanation	Data Type
measurement_type	The method used to measure length. GEODESIC—The shortest line between any two points on the earth's surface on a spheroid (ellipsoid). One use for a geodesic line is to determine the shortest distance between two cities for an airplane's flight path. This is also known as a great circle line if based on a sphere rather than an ellipsoid. GREAT_ELLIPTIC—The line on a spheroid (ellipsoid) defined by the intersection at the surface by a plane that passes through the center of the spheroid and the start and endpoints of a segment. This is also known as a great circle when a sphere is used. LOXODROME—The line follows a single compass bearing, or azimuth. Great circle routes are often broken into a series of loxodromes, which simplifies navigation. This is also known as a rhumb line. PLANAR—Planar measurements use 2D Cartesian mathematics to calculate lengths and areas. This option is only available when measuring in a projected coordinate system and the 2D plane of that coordinate system will be used as the basis for the measurements. Planar measurements reflect the projection of geographic data onto a 2D surface, and do not account for the curvature of the earth. PRESERVE_SHAPE—This type calculates the area or length of the geometry on the surface of the earth ellipsoid, for geometry defined in a projected or geographic coordinate system. This option preserves the shape of the geometry in its coordinate system. (The default value is GEODESIC)	String
units	The units in which the length will be calculated. CENTIMETERS—Centimeters DECIMETERS—Decimeters FEET—Feet INCHES—Inches KILOMETERS—Kilometers METERS—Meters MILES—Miles MILLIMETERS—Millimeters NAUTICALMILES—Nautical Miles YARDS—Yards	String

Return Value

Data Type	Explanation
Double	The length of the feature. By default, for projected coordinate systems, length will be returned in the units of the coordinate system, and for geographic coordinate systems, length will be returned in square meters.

getPart ({index})

Parameter	Explanation	Data Type
index	The index position of the geometry.	Integer

Return Value

Data Type	Explanation
Array	The resultant Array object.

intersect (other, dimension)

Parameter	Explanation	Data Type
other	The second geometry.	Object
dimension	The topological dimension (shape type) of the resulting geometry. 1—A zero-dimensional geometry (point or multipoint). 2—A one-dimensional geometry (polyline). 4—A two-dimensional geometry (polygon).	Integer

Return Value

Data Type	Explanation
Object	A new geometry (point, multipoint, polyline, or polygon) that is the geometric intersection of the two input geometries.

measureOnLine (in_point, {use_percentage})

Parameter	Explanation	Data Type
in_point	A point (PointGeometry or Point) that is used to measure from the start point of the polyline.	PointGeometry
use_percentage	If False, the measure will be returned as a distance; if True, the measure will be returned as a percentage. (The default value is False)	Boolean

Return Value

Data Type	Explanation
Double	A distance or percentage.

overlaps (second_geometry)

Parameter	Explanation	Data Type
second_geometry	A second geometry.	Object

Return Value

Data Type	Explanation
Boolean	A return Boolean value of True indicates the intersection of the two geometries has the same dimension as one of the input geometries.

pointFromAngleAndDistance (angle, distance, {method})

Parameter	Explanation	Data Type
angle	The angle in degrees to the returned point.	Double
distance	The distance in the units of the geometry's spatial reference to the returned point.	Double
method	PLANAR measurements reflect the projection of geographic data onto the 2D surface (in other words, they will not take into account the curvature of the earth). GEODESIC, GREAT_ELLIPTIC, LOXODROME, or PRESERVE_SHAPE measurement types can be chosen as an alternative if desired. GEODESIC—The shortest line between any two points on the earth's surface on a spheroid (ellipsoid). One use for a geodesic line is when you want to determine the shortest distance between two cities for an airplane's flight path. This is also known as a great circle line if based on a sphere rather than an ellipsoid. GREAT_ELLIPTIC—The line on a spheroid (ellipsoid) defined by the intersection at the surface by a plane that passes through the center of the spheroid and the start and endpoints of a segment. This is also known as a great circle when a sphere is used. LOXODROME—A loxodrome is not the shortest distance between two points but instead defines the line of constant bearing, or azimuth. Great circle routes are often broken into a series of loxodromes, which simplifies navigation. This is also known as a rhumb line. PLANAR—Planar measurements use 2D Cartesian mathematics to calculate lengths and areas. This option is only available when measuring in a projected coordinate system, and the 2D plane of that coordinate system will be used as the basis for the measurements. PRESERVE_SHAPE—This type calculates the area or length of the geometry on the surface of the earth ellipsoid for geometry defined in a projected or geographic coordinate system. This option preserves the shape of the geometry in its coordinate system. (The default value is GEODESIC)	String

Return Value

Data Type	Explanation
PointGeometry	Returns a point at a given angle and distance in degrees and meters.

positionAlongLine (value, {use_percentage})

Parameter	Explanation	Data Type
value	The distance along the line. If the distance is less than zero, then the starting point of the line will be returned; if the distance is greater than the length of the line, then the end point of the line will be returned.	Double
use_percentage	The distance may be specified as a fixed unit of measure or a ratio of the length of the line. If True, value is used as a percentage; if False, value is used as a distance. For percentages, the value should be expressed as a double from 0.0 (0%) to 1.0 (100%). (The default value is False)	Boolean

Return Value

Data Type	Explanation
PointGeometry	The point on the line at a specified distance from the beginning of the line.

projectAs (spatial_reference, {transformation_name})

Parameter	Explanation	Data Type
spatial_reference	The new spatial reference. This can be a SpatialReference object or the coordinate system name.	SpatialReference
transformation_name	The geotransformation name.	String

Return Value

Data Type	Explanation
Object	The projected geometry.

queryPointAndDistance (in_point, {as_percentage})

Parameter	Explanation	Data Type
in_point	The input point (PointGeometry or Point).	PointGeometry
as_percentage	If False, the measure will be returned as a distance; if True, the measure will be returned as a percentage. (The default value is False)	Boolean

Return Value

Data Type	Explanation
tuple	Returns a tuple that includes the following: A PointGeometry that is the nearest point on the polyline to the in_point. The distance between the start point of the line and the returned point on the line. The minimum distance between the line and the in_point. A Boolean that indicates if the in_point is on the right side of the line. The direction of the line determines the right and left sides.

segmentAlongLine (start_measure, end_measure, {use_percentage})

Parameter	Explanation	Data Type
start_measure	The starting distance from the beginning of the line.	Double
end_measure	The ending distance from the beginning of the line.	Double
use_percentage	The start and end measures may be specified as fixed units or as a ratio. If True, start_measure and end_measure are used as a percentage; if False, start_measure and end_measure are used as a distance. For percentages, the measures should be expressed as a double from 0.0 (0 percent) to 1.0 (100 percent). (The default value is False)	Boolean

Return Value

Data Type	Explanation
PolyLine	The segment of the line between two points.

snapToLine (in_point)

Parameter	Explanation	Data Type
in_point	A point (PointGeometry or Point) to be snapped to the line.	PointGeometry

Return Value

Data Type	Explanation
PointGeometry	The snapped point.

symmetricDifference (other)

Parameter	Explanation	Data Type
other	A second geometry.	Object

Return Value

Data Type	Explanation
Object	The resulting geometry.

touches (second_geometry)

Parameter	Explanation	Data Type
second_geometry	A second geometry.	Object

Return Value

Data Type	Explanation
Boolean	A return Boolean value of True indicates the boundaries of the geometries intersect.

union (other)

Parameter	Explanation	Data Type
other	A second geometry.	Object

Return Value

Data Type	Explanation
Object	The resulting geometry.

within (second_geometry, {relation})

Parameter	Explanation	Data Type
second_geometry	A second geometry.	Object
relation	The spatial relationship type. BOUNDARY— Relationship has no restrictions for interiors or boundaries. CLEMENTINI— Interiors of geometries must intersect. Specifying CLEMENTINI is equivalent to specifying None. This is the default. PROPER— Boundaries of geometries must not intersect. (The default value is None)	String

Return Value

Data Type	Explanation
Boolean	A return Boolean value of True indicates this geometry is contained within the second geometry.

Code sample

Polyline example

Create a polyline feature class from scratch.

import arcpy

# A list of features and coordinate pairs
feature_info = [[[1, 2], [2, 4], [3, 7]],
                [[6, 8], [5, 7], [7, 2], [9, 5]]]

# A list that will hold each of the Polyline objects
features = []

for feature in feature_info:
    # Create a Polyline object based on the array of points
    # Append to the list of Polyline objects
    features.append(
        arcpy.Polyline(
            arcpy.Array([arcpy.Point(*coords) for coords in feature])))

# Persist a copy of the Polyline objects using CopyFeatures
arcpy.CopyFeatures_management(features, "c:/geometry/polylines.shp")