togo 0.3.3

Lightweight Python bindings for the TG geometry library

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.

Note on pronunciation: "ToGo" is pronounced like the country Togo ("TOH-go"), not like "to go".

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. ToGo's API is flexible and allows you to reason in either TG concepts (if you're familiar with the TG library) or Shapely conventions (the de facto standard for geospatial work in Python)—whichever fits your workflow best.

See SHAPELY_API.md for more details on Shapely compatibility.

Installation

pip install togo

Features

• Fast and efficient geometric operations
• Support for standard geometry types: Point, Line, Ring, Polygon, and their multi-variants
• Flexible API supporting both TG and Shapely conventions
• 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
• Advanced operations via libgeos integration (buffer, unary union, simplify, centroid, convex_hull, etc.)
• Distance and proximity operations (nearest_points, shortest_line)

Basic Usage

ToGo's API supports multiple styles of interaction. You can use Shapely-like conventions for familiarity, TG-like conventions if you're already familiar with that library, or mix both as needed.

Creating Geometries

from togo import Point, LineString, Polygon, Ring, Poly, Geometry

# Shapely-like syntax
point = Point(1.0, 2.0)
line = LineString([(0, 0), (1, 1), (2, 2)])
poly = Polygon([(0, 0), (4, 0), (4, 4), (0, 4), (0, 0)])

# TG-like syntax with Ring and Poly
ring = Ring([(0,0), (10,0), (10,10), (0,10), (0,0)])
polygon = Poly(ring)

# Direct Geometry creation from formats
geom = Geometry("POINT(1 2)", fmt='wkt')
geom2 = Geometry('{"type":"Point","coordinates":[1,2]}', fmt='geojson')

Working with Geometries

from togo import Point, Polygon

# Access properties (works with both API styles)
point = Point(1.0, 2.0)
print(point.geom_type)     # 'Point'
print(point.bounds)        # (1.0, 2.0, 1.0, 2.0)

poly = Polygon([(0, 0), (4, 0), (4, 4), (0, 4), (0, 0)])
print(poly.area)           # 16.0
print(poly.length)         # 16.0

# Convert between formats
print(point.to_wkt())      # 'POINT (1 2)'
print(point.to_geojson())  # '{"type":"Point","coordinates":[1.0,2.0]}'

# Spatial predicates
if poly.contains(point):
    print("Polygon contains point!")

# Centroid (Shapely-compatible)
centroid = poly.centroid  # Returns a Point geometry
print(centroid.to_wkt())  # e.g., 'POINT (2 2)'

# Convex hull (Shapely-compatible)
from togo import convex_hull
concave_poly = Polygon([(0, 0), (2, 0), (2, 2), (1, 1), (0, 2), (0, 0)])
hull = convex_hull(concave_poly)
print(hull.to_wkt())  # 'POLYGON((0 0,2 0,2 2,0 2,0 0))'

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.length}")

# 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

Integration with tgx and libgeos

Togo integrates with the tgx extension and libgeos to provide advanced geometry operations, such as topological unions and conversions between TG and GEOS geometry formats. This allows you to leverage the speed of TG for basic operations and the flexibility of GEOS for more complex tasks.

Example: Unary Union (GEOS integration)

The unary_union method demonstrates this integration. It combines multiple geometries into a single geometry using GEOS's topological union, with all conversions handled automatically:

from togo import Geometry, Point, Poly, Ring

# Create several polygons
poly1 = Poly(Ring([(0,0), (2,0), (2,2), (0,2), (0,0)]))
poly2 = Poly(Ring([(1,1), (3,1), (3,3), (1,3), (1,1)]))

# Perform unary union (requires tgx and libgeos)
union = Geometry.unary_union([poly1, poly2])

# The result is a single geometry representing the union of the input polygons
print(union.to_wkt())

This operation uses tgx to convert TG geometries to GEOS, applies the union in libgeos, and converts the result back to TG format for further use in ToGo.

Example: Buffer Operations (GEOS integration)

The buffer() method creates geometrical buffers (expanded or shrunk versions of geometries) using GEOS:

from togo import Point, LineString, Polygon, Ring, Geometry

# Buffer a point to create a circular zone
point = Point(0, 0)
circular_zone = point.buffer(10.0, quad_segs=16)
print(f"Point buffer: {circular_zone.geom_type}")  # Polygon

# Buffer a line to create a corridor around it
line = LineString([(0, 0), (10, 10)])
corridor = line.buffer(2.0, cap_style=1)  # round ends
print(f"Line buffer: {corridor.geom_type}")  # Polygon

# Buffer a polygon to expand or shrink it
exterior = Ring([(0, 0), (10, 0), (10, 10), (0, 10), (0, 0)])
poly = Polygon(exterior)

expanded = poly.buffer(2.0)    # Expand outward by 2 units
shrunk = poly.buffer(-1.0)     # Shrink inward by 1 unit

# Via Geometry object with advanced parameters
geom = Geometry("POLYGON((0 0, 20 0, 20 20, 0 20, 0 0))")
buffered = geom.buffer(
    distance=3.0,
    quad_segs=16,           # Segments per quadrant (higher = smoother)
    cap_style=1,            # 1=round, 2=flat, 3=square
    join_style=1,           # 1=round, 2=mitre, 3=bevel
    mitre_limit=5.0         # Mitre ratio limit
)

Like unary_union, buffer operations automatically handle TG ↔ GEOS conversions. For comprehensive buffer documentation, see BUFFER_API.md.

Example: Distance and Proximity Operations (GEOS integration)

The nearest_points() and shortest_line() functions find the closest points between geometries:

from togo import Point, LineString, Polygon, Ring, nearest_points, shortest_line, from_wkt

# Find nearest points between geometries (module-level function)
point = Point(0, 0)
line = LineString([(10, 0), (10, 10)])
pt1, pt2 = nearest_points(point, line)
print(f"Nearest on point: ({pt1.x}, {pt1.y})")  # (0.0, 0.0)
print(f"Nearest on line: ({pt2.x}, {pt2.y})")   # (10.0, 0.0)

# Get the connecting line (Shapely v2 API - module-level function)
shortest = shortest_line(point, line)
print(f"Distance: {shortest.length}")  # 10.0
print(f"Connecting line: {shortest.coords}")  # [(0.0, 0.0), (10.0, 0.0)]

# Method style also works
shortest = point.shortest_line(line)
pt1, pt2 = point.nearest_points(line)

# Measure gap between polygons
poly1 = Polygon(Ring([(0, 0), (5, 0), (5, 5), (0, 5), (0, 0)]))
poly2 = Polygon(Ring([(10, 0), (15, 0), (15, 5), (10, 5), (10, 0)]))
gap_line = shortest_line(poly1, poly2)
print(f"Gap between polygons: {gap_line.length}")  # 5.0

# Practical use case: Check if features are within distance
def within_distance(geom1, geom2, max_dist):
    return shortest_line(geom1, geom2).length <= max_dist

building1 = Polygon(Ring([(0, 0), (10, 0), (10, 10), (0, 10), (0, 0)]))
building2 = Polygon(Ring([(20, 0), (30, 0), (30, 10), (20, 10), (20, 0)]))

if within_distance(building1, building2, 15):
    print("Buildings meet separation requirement")

# Works with WKT geometries
g1 = from_wkt("POINT(0 0)")
g2 = from_wkt("LINESTRING(5 5, 10 10)")
connecting = shortest_line(g1, g2)
print(f"Distance: {connecting.length:.2f}")

For detailed documentation, see SHORTEST_LINE_QUICK_REFERENCE.md. For more examples, see examples/shortest_line_demo.py.

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
• Buffer operations support quad_segs parameter to balance quality vs. performance

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