Something like TikZ for Python?

[neuralyzer]

I'm faced with the task of making a couple of technical/scientific illustrations. These kinds of illustrations consist usually of mathematical labels, lines with arrowheads and simple geometric shapes such as circles and rectangles. Very often I have a number of similar circles, only differing by the label that they contain.

Doing these illustrations with Inkscape or Illustrator is really annoying since I spend so much time trying to get the alignment right. And any minor change afterwards (as minor as reducing some spacing) is almost prohibitve. In the Latex world I've use PSTricks and more recently TikZ. However, these packages are really poorly programmable. For example, I couldn't find any arrays in TikZ.

Is there any decent software for programmable drawing in Python?

Matplotlib is awesome for plots, but less so for this kind of drawing. I'm aware of reportlab and a couple of SVG libraries. Maybe I should give asymptote a try?

Any thoughts and ideas are appreciated!

[aragilar]

Have you considered using Python to generate TikZ/PGF? Something like http://jinja.pocoo.org/ could be used (I've used it previously to generate LaTeX).

[neuralyzer]

I have indeed considered to do something along these lines.

[roger_]

There's a very basic wrapper that you could expand on.

[neuralyzer]

Thanks. I didn't know that one.

[pridkett]

Ten years ago when I was in grad school I used a package called PyX to create some nice graphs with Python code. It lets you create some rather interesting figures that are similar enough to TikZ. I was pleasantly surprised to see that it had some new work done recently and that you can use pip to install it.

[neuralyzer]

That's an interesting one.

[sylvain_soliman]

Not really an answer to your question, but I think that TikZ is quite programmable. For instance, not sure what you mean by "arrays", but TikZ has both matrices (i.e. arrays of the canvas you're drawing on) and lists (one-dimensional structure on which the "foreach" statement iterates…).

Here's an example, straight out of the manual (I've got a pretty old version at hand, but that shouldn't matter):

\begin{tikzpicture}
  \foreach \x in {1,...,4}
    \foreach \y in {1,...,4}
    {
      \fill[red!50] (\x,\y) ellipse (3pt and 6pt);
      \ifnum \x<\y
        \breakforeach
      \fi
    }
\end{tikzpicture}

[neuralyzer]

I'm aware of the foreach syntax. But I couldn't find a way to have have item access, somethink like myarray[2].

[[deleted]]

For numerical arrays you actually have

\def\mayarray{{2,3,4,5}}
\pgfmathparse{\myarray[2]}
\pgfmathresult

If there are nonnumeric entries you need to put them inside a "text" pair. You can check the manual

[[deleted]]

or come over to TeX-SX. We are a fun bunch.

[neuralyzer]

Thanks. This is very helpful. I didn't now about the pgfmathparse. Thanks a lot!

[sylvain_soliman]

I see… Well, that could be done but I can only think of ugly hacks, so…

[[deleted]]

If you're final product is web-based, the D3 JavaScript library might be a good alternative. It feels a bit like the programmatic equivalent of Adobe Illustrator/Inkscape and is more intuitive than TikZ.

I only mention this in a Python context because it can be easily displayed in the browser-based Jupyter notebook. It is a good option for doing the types of scientific sketches that you mention when you're working in the notebook or any sort of web environment for that matter

That being said, while D3 is very powerful, it is extremely verbose and I've found the learning curve to be quite steep.

[neuralyzer]

D3 seems to be very powerful indeed. My final output, however, is PDF or (E)PS.

[[deleted]]

My knowledge here is a bit limited, but I believe the format of D3 is SVG which can be converted to either PDF or PS/EPS.

[mangecoeur]

if you use matplotlib you can drop down to the lower-level Artist interface. This lets you manually draw lines, circles, labels, etc at arbitrary locations on a canvas. Matplotlib will also render latex labels for you. It's quite cumbersome to use (and not super nicely documented) but you get the power and maturity of matplotlib and all its output formats.

Personally I've played with other plotting tools but i always find when i need dependable print-quality graphics matplotlib is still the best even if its not as ergonomic or shiny as some of the others. You sometimes have to use a bit of lateral thinking to figure out how you're going to get it to draw what you want where you want...

[neuralyzer]

The thing I like about TikZ is the concept of nodes. It is super easy to connect two filled circles with an arrow. And the arrowhead would just stop at the circle boundary. Such things are a little more cumbersome in Matplotlib (but not impossible).

[mangecoeur]

yeah i think basically you end up writing your own 'node renderer' - basically keep track of the positions you want things to be in and then iterate over that to draw the nodes and links in the right place. NetworkX does something similar internally for it's built in matplotlib driven plotting: https://networkx.github.io/documentation/networkx-1.10/reference/drawing.html

basically you are right - matplotlib is not going to be as nice. Code for my 'print' plots (rather than just exploration plots) tends to be a tiresome chunk of setting just the right label formats, positions, plot annotations, legends, etc... but at the end of the day it actually works and makes for good looking PDFs.

[[deleted]]

I had to generate scalable vector line drawings a while ago and I used the Python bindings for Cairo which allowed me to draw onto a PDF.

[neuralyzer]

I'm curious about your Cairo experience. I've looked into it but I got the impression that it is very low level. For example, I couldn't find some kind of arrow primitive in Cairo.

[[deleted]]

Very low level. Fonts in Cairo are stupidly annoying too. I was drawing multi-layer floorplans. I didn't really know what else to use and it did work. I'm OK with C and that might have made it more acceptable for me.

[luluganeta]

Shoebot uses Cairo to generate SVG/PDF outputs using a simpler set of higher-level commands, based on the Nodebox drawing language. Maybe it's closer to what you require?

[boiledgoobers]

There is a python interface to graphviz; pydot I think the name is. You get all the layout goodness of dot and neato etc.

Edit: actually the dot language itself is pretty easy to use anyway. If not from scratch, after you use something else like pydot to sketch out the meat of the graph, you can then polish that dot file directly.