API conventions

planex2d uses a few conventions throughout its Python API.

Chaining and copies

Methods that change an object in place return that object, so calls can be chained. The method of the same name ending in -ed returns a new object and leaves the original unchanged: Rotate and Rotated, Translate and Translated.

Reading the arguments

Positional arguments read from … to …. Line(a, b) draws a line from a to b, and Constrain("Line.1", "Line.2", px.Tangent) makes Line.1 tangent to Line.2. Sizes follow the ends, as in Slot(l, w), and flags such as px.Horizontal come last, in any order. Keywords are options with values, such as name=, id= or until=.

A drawing call in a sketch starts at the pen when the start is left out. The pen’s direction is used only where nothing else fixes the curve:

Call	Reads as
`Line(4)`	4 along the pen’s direction
`Line(3, 4)`	From the pen, 3 along h and 4 along v
`Line((3, 4))`	From the pen to the point (3, 4)
`Line((1, 0), (3, 4))`	From (1, 0) to (3, 4)
`Arc((3, 4))`	From the pen to (3, 4), tangent to the pen’s direction
`Line("Line.2", through=(5, 3))`	From the pen through (5, 3) to where that line meets Line.2
`Line((0, 2), parallel="Line.1", until="Line.2")`	From (0, 2), parallel to Line.1, up to Line.2
`Arc((5, 0), sweep=90, center=(0, 0))`	From (5, 0), a quarter turn about the origin

A helper that fixes the carrier, such as through=, parallel=, perpendicular=, angle= or tangent=, leaves both readings as they are. A helper that gives the end, until= or sweep=, takes the place of the end, so a single positional argument is then the start. An element as an end needs a helper that fixes the carrier. Without one, the call raises and names the helpers it accepts.

Points

A point in the plane is a pair (h, v), given as a tuple, a list or a NumPy row, and a set of points is an array of shape (n, 2). A 3D point (x, y, z) is accepted as well when it lies in the plane; off the plane, the call raises. In a sketch, a point can also be a point id such as "A" or "Line.1.end", or the pen, sk.pen. Where a call needs an end, an element or another target stands for the point where the carrier meets it, and (target, point) picks the intersection nearest that point.

Planes

Every argument that takes a plane accepts a px.Plane or anything that has a plane: a sketch, a face, a shape, a wire, a compound or a planar OpenCASCADE shape. None means the xy plane, px.XY. netgen’s occ.Axes is accepted wherever a plane is, so code written for netgen passes its axes unchanged, and 3D points and directions also take netgen’s Pnt, Vec and Dir.

Angles and units

Angles are in degrees. planex2d does not impose a unit system: lengths use whatever unit you choose, as long as you use it consistently. See Units.

Queries

Query methods return plain values: numbers, dictionaries or arrays, depending on the query.

Errors and warnings

A call that cannot perform the requested operation raises an exception that explains why. A valid result that may be unexpected produces a px.PlanexWarning. The library does not silently correct such cases. To make warnings fail explicitly, for example in automated studies, use Python’s warnings module:

[1]:

import warnings
import planex as px

warnings.simplefilter("error", px.PlanexWarning)

For installation requirements and optional dependencies, see Installation.