togo 0.1.3

Lightweight Python bindings for the TG geometry library

ToGo

Python bindings for TG (Geometry library for C - Fast point-in-polygon)

ToGo is a high-performance Python library for computational geometry, providing a Cython wrapper around the above-mentioned C library.

The main goal is to offer a Pythonic, object-oriented, fast and memory-efficient library for geometric operations, including spatial predicates, format conversions, and spatial indexing.

While ToGo's API interfaces are still a work in progress, the underling C library is stable and well-tested.

Installation

pip install togo

Features

• Fast and efficient geometric operations
• Support for standard geometry types: Point, Line, Ring, Polygon, and their multi-variants
• Geometric predicates: contains, intersects, covers, touches, etc.
• Format conversion between WKT, GeoJSON, WKB, and HEX
• Spatial indexing for accelerated queries
• Memory-efficient C implementation with Python-friendly interface

Basic Usage

from togo import Geometry, Point, Ring, Poly

# Create a geometry from GeoJSON
geom = Geometry('{"type":"Point","coordinates":[1.0,2.0]}')

# Create a point
point = Point(1.0, 2.0)

# Create a polygon
ring = Ring([(0,0), (10,0), (10,10), (0,10), (0,0)])
polygon = Poly(ring)

# Convert to various formats
wkt = polygon.as_geometry().to_wkt()
geojson = polygon.as_geometry().to_geojson()

# Perform spatial predicates
point_geom = point.as_geometry()
contains = polygon.as_geometry().contains(point_geom)

Core Classes

Geometry

The base class that wraps tg_geom structures and provides core operations:

# Create from various formats
g1 = Geometry('POINT(1 2)', fmt='wkt')
g2 = Geometry('{"type":"Point","coordinates":[1,2]}', fmt='geojson')

# Geometric predicates
g1.intersects(g2)
g1.contains(g2)
g1.within(g2)

# Format conversion
g1.to_wkt()
g1.to_geojson()

# Access sub-geometries by index (e.g., for GeometryCollection, MultiPoint, etc.)
gc = Geometry('GEOMETRYCOLLECTION(POINT(1 2),POINT(3 4))', fmt='wkt')
first = gc[0]  # Bound to TG function call tg_geom_geometry_at(idx)
second = gc[1]
print(first.type_string())  # 'Point'

Point

from togo import Point

# Create a point
p = Point(1.0, 2.0)

# Access coordinates
print(f"X: {p.x}, Y: {p.y}")

# Get as a tuple
print(p.as_tuple())

# Convert to a Geometry object
geom = p.as_geometry()
print(geom.type_string())

Segment

from togo import Segment, Point

# Create a segment from two points (or tuples)
seg = Segment(Point(0, 0), Point(1, 1))
# Or using tuples
tuple_seg = Segment((0, 0), (1, 1))

# Access endpoints
print(seg.a)  # Point(0, 0)
print(seg.b)  # Point(1, 1)

# Get the bounding rectangle
rect = seg.rect()
print(rect)  # ((0.0, 0.0), (1.0, 1.0))

# Check intersection with another segment
other = Segment((1, 1), (2, 2))
print(seg.intersects(other))  # True or False

Line

from togo import Line

# Create a line from a list of tuples
line = Line([(0,0), (1,1), (2,0)])

# Get number of points
print(f"Number of points: {line.num_points()}")

# Get all points as a list of tuples
print(f"Points: {line.points()}")

# Get the length of the line
print(f"Length: {line.length()}")

# Get the bounding box
print(f"Bounding box: {line.rect()}")

# Get a point by index
print(f"First point: {line[0].as_tuple()}")

Ring

from togo import Ring

# Create a ring (must be closed)
ring = Ring([(0,0), (10,0), (10,10), (0,10), (0,0)])

# Get area and perimeter
print(f"Area: {ring.area()}")
print(f"Perimeter: {ring.perimeter()}")

# Check if it's convex or clockwise
print(f"Is convex: {ring.is_convex()}")
print(f"Is clockwise: {ring.is_clockwise()}")

# Get bounding box
min_pt, max_pt = ring.rect().min, ring.rect().max
print(f"Bounding box: {min_pt.as_tuple()}, {max_pt.as_tuple()}")

Poly

from togo import Poly, Ring, Point

# Create a polygon with one exterior ring and one interior hole
exterior = Ring([(0,0), (10,0), (10,10), (0,10), (0,0)])
hole1 = Ring([(1,1), (2,1), (2,2), (1,2), (1,1)])
poly = Poly(exterior, holes=[hole1])

# Get the exterior ring
ext_ring = poly.exterior()
print(f"Exterior has {ext_ring.num_points()} points")

# Get number of holes
print(f"Number of holes: {poly.num_holes()}")

# Get a hole by index
h = poly.hole(0)
print(f"Hole area: {h.area()}")

# A polygon is a geometry, so you can use geometry methods
geom = poly.as_geometry()
print(f"Contains point (5,5): {geom.contains(Point(5,5).as_geometry())}")
# Point is inside the hole, so it is not contained by the polygon
print(f"Contains point (1.5,1.5): {geom.contains(Point(1.5,1.5).as_geometry())}")

MultiGeometries

Creating collections of geometries:

from togo import Geometry, Point, Line, Poly, Ring

# Create a MultiPoint
multi_point = Geometry.from_multipoint([(0,0), (1,1), Point(2,2)])

# Create a MultiLineString
multi_line = Geometry.from_multilinestring([
    [(0,0), (1,1)],
    Line([(2,2), (3,3)])
])

# Create a MultiPolygon
poly1 = Poly(Ring([(0,0), (1,0), (1,1), (0,1), (0,0)]))
poly2 = Poly(Ring([(2,2), (3,2), (3,3), (2,3), (2,2)]))
multi_poly = Geometry.from_multipolygon([poly1, poly2])

Polygon Indexing

Togo supports different polygon indexing strategies for optimized spatial operations:

from togo import TGIndex, set_polygon_indexing_mode

# Set the indexing mode
set_polygon_indexing_mode(TGIndex.NATURAL)  # or NONE, YSTRIPES

Performance Considerations

• Togo is optimized for speed and memory efficiency
• For large datasets, proper indexing can significantly improve performance
• Creating geometries with the appropriate format avoids unnecessary conversions

Soon there will be a full API documentation, for now please refer to the test suite for more usage examples.