matplotlib.patches.Arc¶

class
matplotlib.patches.
Arc
(xy, width, height, angle=0.0, theta1=0.0, theta2=360.0, **kwargs)[source]¶ Bases:
matplotlib.patches.Ellipse
An elliptical arc, i.e. a segment of an ellipse.
Due to internal optimizations, there are certain restrictions on using Arc:
 The arc cannot be filled.
 The arc must be used in an
Axes
instanceit can not be added directly to aFigure
because it is optimized to only render the segments that are inside the axes bounding box with high resolution.
Parameters:  xy(float, float)
The center of the ellipse.
 widthfloat
The length of the horizontal axis.
 heightfloat
The length of the vertical axis.
 anglefloat
Rotation of the ellipse in degrees (counterclockwise).
 theta1, theta2float, optional
Starting and ending angles of the arc in degrees. These values are relative to angle, e.g. if angle = 45 and theta1 = 90 the absolute starting angle is 135. Default theta1 = 0, theta2 = 360, i.e. a complete ellipse. The arc is drawn in the counterclockwise direction. Angles greater than or equal to 360, or smaller than 0, are represented by an equivalent angle in the range [0, 360), by taking the input value mod 360.
Other Parameters:  **kwargs
Patch
properties Most
Patch
properties are supported as keyword arguments, with the exception of fill and facecolor because filling is not supported.Property Description agg_filter
a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array alpha
float or None animated
bool antialiased
or aaunknown capstyle
{'butt', 'round', 'projecting'} clip_box
Bbox
clip_on
bool clip_path
Patch or (Path, Transform) or None color
color contains
callable edgecolor
or eccolor or None or 'auto' facecolor
or fccolor or None figure
Figure
fill
bool gid
str hatch
{'/', '\', '', '', '+', 'x', 'o', 'O', '.', '*'} in_layout
bool joinstyle
{'miter', 'round', 'bevel'} label
object linestyle
or ls{'', '', '.', ':', '', (offset, onoffseq), ...} linewidth
or lwfloat or None path_effects
AbstractPathEffect
picker
None or bool or float or callable rasterized
bool or None sketch_params
(scale: float, length: float, randomness: float) snap
bool or None transform
Transform
url
str visible
bool zorder
float

draw
(self, renderer)[source]¶ Draw the arc to the given renderer.
Notes
Ellipses are normally drawn using an approximation that uses eight cubic Bezier splines. The error of this approximation is 1.89818e6, according to this unverified source:
Lancaster, Don. Approximating a Circle or an Ellipse Using Four Bezier Cubic Splines.
There is a use case where very large ellipses must be drawn with very high accuracy, and it is too expensive to render the entire ellipse with enough segments (either splines or line segments). Therefore, in the case where either radius of the ellipse is large enough that the error of the spline approximation will be visible (greater than one pixel offset from the ideal), a different technique is used.
In that case, only the visible parts of the ellipse are drawn, with each visible arc using a fixed number of spline segments (8). The algorithm proceeds as follows:
The points where the ellipse intersects the axes bounding box are located. (This is done be performing an inverse transformation on the axes bbox such that it is relative to the unit circle  this makes the intersection calculation much easier than doing rotated ellipse intersection directly).
This uses the "line intersecting a circle" algorithm from:
Vince, John. Geometry for Computer Graphics: Formulae, Examples & Proofs. London: SpringerVerlag, 2005.
The angles of each of the intersection points are calculated.
Proceeding counterclockwise starting in the positive xdirection, each of the visible arcsegments between the pairs of vertices are drawn using the Bezier arc approximation technique implemented in
matplotlib.path.Path.arc()
.