Shapes in Python
How to make SVG shapes in python. Examples of lines, circle, rectangle, and path.
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Adding Lines and Polygons to Figures¶
As a general rule, there are two ways to add shapes (lines or polygons) to figures:
- Trace types in the
scatterfamily (e.g.scatter,scatter3d,scattergeoetc) can be drawn withmode="lines"and optionally support afill="self"attribute, and so can be used to draw open or closed shapes on figures. - Standalone lines, ellipses and rectangles can be added to figures using
fig.add_shape(), and they can be positioned absolutely within the figure, or they can be positioned relative to the axes of 2d cartesian subplots i.e. in data coordinates.
Note: there are special methods add_hline, add_vline, add_hrect and add_vrect for the common cases of wanting to draw horizontal or vertical lines or rectangles that are fixed to data coordinates in one axis and absolutely positioned in another.
The differences between these two approaches are that:
- Traces can optionally support hover labels and can appear in legends.
- Shapes can be positioned absolutely or relative to data coordinates in 2d cartesian subplots only.
- Traces cannot be positioned absolutely but can be positioned relative to data coordinates in any subplot type.
- Traces also support optional text, although there is a textual equivalent to shapes in text annotations.
Shape-drawing with Scatter traces¶
There are two ways to draw filled shapes: scatter traces and layout.shapes which is mostly useful for the 2d subplots, and defines the shape type to be drawn, and can be rectangle, circle, line, or path (a custom SVG path). You also can use scatterpolar, scattergeo, scattermapbox to draw filled shapes on any kind of subplots. To set an area to be filled with a solid color, you need to define Scatter.fill="toself" that connects the endpoints of the trace into a closed shape. If mode=line (default value), then you need to repeat the initial point of a shape at the end of the sequence to have a closed shape.
import plotly.graph_objects as go
fig = go.Figure(go.Scatter(x=[0,1,2,0], y=[0,2,0,0], fill="toself"))
fig.show()
You can have more shapes either by adding more traces or interrupting the series with None.
import plotly.graph_objects as go
fig = go.Figure(go.Scatter(x=[0,1,2,0,None,3,3,5,5,3], y=[0,2,0,0,None,0.5,1.5,1.5,0.5,0.5], fill="toself"))
fig.show()