Develop Reference

Graphically displaying some sets contents and their relations between elements: Dedicated module? Nodes/edges graph and ellipses drawing?

To understand better mathematics and for further use, I need to solve some exercises or represent myself some concepts using my computer, by programming them and watch their results on screen.
Among the subjects I'm studying, are the sets and their elements, inclusions, injections, etc.
I'd like to represent them graphically with Python. But not to loose myself in details, plotting circles for elements and lines with arrows for relations, as if I was using Logo.
Use a known module instead, to help me doing my displays would be perfect.
Is there any tool useful to represent graphically some sets and their content with Python?
If not, I guess that they are some tools that represent graphs, and then translating:
elements -> nodes
relations -> edges
could do the work, provided I draw an ellipse around each set...?
another better way to achieve this?
Which tool would you recommend me to represent sets graphically with Python?

Generate schematic (geographic) diagram from graph

I would like to know how best to generate a schematic diagram, something like this, from a graph (created using the Python NetworkX library) that contains the latitude and longitude of each node (city) and the lines connecting them in the Indian railway network.
The cities (nodes) should be located reasonably close to their actual position, but not necessarily exactly. I am OK with using the plate carrée projection that simply maps lat/long onto X/Y in the diagram.
The rail lines (edges) can be straight lines or even curves if it fits better.
On the diagram should be displayed the cities (preferably as dots) along with a short (max 4 characters) label for each, the lines connecting them, and a single label for each line (the given example has quite long labels for the lines).
Preferably the amount of manual tweaking of coordinates to get things to fit should be minimised.
Using Graphviz was my first idea. But I don't know how well neato/fdp (required for fixed positioning of nodes) will perform with large numbers of nodes/edges. Also, making Graphviz display labels separately outside the nodes (rather than inline) seems to need a lot of manual positioning of each label, which would be pretty boring. Is there any better way to get this kind of layout?

Doable (https://forum.graphviz.org/t/another-stupid-graphviz-trick-geographic-graphs/256), but does not seem to use many Graphviz features. In addition to tools mentioned in the link, maybe consider pikchr (https://pikchr.org/home/doc/trunk/homepage.md)

A framework for animating a network graph algorithm in Python

I’m looking for a way to animate a network graph algorithm in Python.
What I need to do is to draw a (large) network graph and manipulate it (add/remove vertices, add/remove edges, change vertices size and/or color, change edges colors, etc.), without having to redraw the entire graph for every frame.
I found several similar questions (this one for example) but they all either regard static plotting of network graphs or are very old and the examples doesn't work.

3Blue1Brown's manim animation engine may be something to consider. It supports LaTeX-style graphics and has quite an active community.

Python script to uncurl or unfold geometry along a curve

I have been all over the internet trying to find the answer to this one and I've reached the end of my patience. What I am trying to achieve is pretty much what the standard bend deformer does but the only difference is I want it to unfold along a pre-defined curve. There are literally hundreds of tutorials about the bend deformer all doing the same thing, unfolding along a flat plane but none on how to do it along a curved surface. I have also tried paint effects with control curves to no avail and baking the bend deformer into the geometry then curving it afterwards. This last option didn't work as I no longer had the control I required. It seems from my search that probably the only way to do this would be through a Mel or Python script and I was wondering would anyone be able to help?

something like this?
Constrain -> Motion Patch -> Attach to Motion Patch + Flow Path Object

Lattice deformers themselves are skinnable, so you can run a skeleton or bend deformer through a lattice to maniuplate it's shape. This will also let you control the twist along the deformation. Animate the object you want to deform into the area of influence of the lattice to create the follow effect, while animating the deformation of the lattice itself at the same time to create the follow effect.
Or, you can just make the lattice follow the path using a spline IK control.

Arched Relationship Infographic In Python

This is a very specific inforgraphic challange altough the fundemental question is how do you build archs between words using matplotlib, cario or an other python libary.
Given a the following data structure.
me, you, 7 |
me, apple, 9 |
apple, you, 1 |
bike, me, 5
Names would be displayed horizontally the names with the most relationships larger than the others and then there would be weighted archs between the names. A 10 weighted arch would be twice as thick as a 5 weighted arch.
Inspiration comes from: similar diverstiy. http://similardiversity.net/
Let the challange commence!

matplotlib isn't the right library here, since it's not a general purpose graphics library. What you need here is either something like Cairo, or much simpler, you can do with the graphics capabilities of any GUI toolkit, such as PyQt. Another feasible approach is PyGame, which has good drawing capabilities as well.
If you want an example, see this Cairo samples page, the first sample - arc. You just write the text words and then use the arc code for an arc of any width and color between them.

There are several libraries, at least one of which relies on Matplotlib, that will do what you want. I recommend Networkx (www.networkx.lanl.gov) to build your graph structure, and which you can then use to call the relevant Matplotlib methods to plot. Networkx and Matplotlib work very well together.
import networkx as NX
import matplotlib.pyplot as PLT
Gh = NX.Graph()
Gh.add_edge("You", "Bike", weight=1.0)
Gh.add_edge("Bike", "Apple", weight=0.9)
Gh.add_edge("Me", "Bike", weight=1.1)
all_nodes = Gh.nodes()
# to scale node size with degree:
scaled_node_size = lambda(node) : NX.degree(Gh, node) * 700
position = NX.spring_layout(Gh) # just choose a layout scheme
NX.draw_networkx_nodes(Gh, position, node_size=map(scaled_node_size, all_nodes))
NX.draw_network_edges(Gh, position, Gh.edges(), width=1.0, alpha=1.0, edge_color="red")
# now for the Matplotlib part:
PLT.axis("off")
PLT.show()
As you can see, you could scale the edges by applying a factor to vary the 'weight' parameter to any of the 'edge' methods, just the same way as i did it for node scaling.
I would also recommend pygraphviz (obviously using graphviz as its backend). It is very similar to Netwworkx (same lead developer).

I don't really see where the difficulty or challenge is. All you need is a graphics library that can draw text and half circles, which is possible in pretty much everything. There is no need for Bezier curves. For example you could simply create an SVG file (then you don't even need any library and can nicely embed this in a webpage and use some JavaScript to make it interactive).
The actual plotting is simple: the center of a circle is in the middle between the two words, the radius is half the distance between them. You can then adjust the stroke to reflect other quantities.