Skip to main content

PyCon: Managing Complexity (and Testing)

Managing Complexity (and Testing)

This was a talk on various metrics for code complexity.

Knowing the number of lines of code is not enough. For instance, how many of those lines are well tested? sloccount is a project to count lines of code.

The number of unittests that a project has is also not enough information.

There are many approaches to testing code coverage. For instance, do your tests test every line? Every branch? Every path? Each of these is successively harder. Even 100% path coverage doesn't guarantee you have no bugs.

Your gut feeling for how much code coverage you have is usually too optimistic.

Remember that human brains have not kept up with Moore's law ;)

He mentioned McCabe complexity as a way to measure code complexity.

Complexity != length. A function can be very long without being complex. This is the case if it has no if statements, no loops, no early returns, etc.

There is no way to test path coverage in Python.

He mentioned PyMetrics as a Python package to test code complexity. It was written by Reg Charney, a fellow member of BayPiggies.

High code complexity is correlated with a high bug count. Duh! ;)

Dead and redundant code is 40-100% more likely to be buggy.

Halstead is another metric, but the speaker said it was difficult for him to understand.

Code reviews are good.

Figleaf is a tool for testing code coverage.


Popular posts from this blog

Ubuntu 20.04 on a 2015 15" MacBook Pro

I decided to give Ubuntu 20.04 a try on my 2015 15" MacBook Pro. I didn't actually install it; I just live booted from a USB thumb drive which was enough to try out everything I wanted. In summary, it's not perfect, and issues with my camera would prevent me from switching, but given the right hardware, I think it's a really viable option. The first thing I wanted to try was what would happen if I plugged in a non-HiDPI screen given that my laptop has a HiDPI screen. Without sub-pixel scaling, whatever scale rate I picked for one screen would apply to the other. However, once I turned on sub-pixel scaling, I was able to pick different scale rates for the internal and external displays. That looked ok. I tried plugging in and unplugging multiple times, and it didn't crash. I doubt it'd work with my Thunderbolt display at work, but it worked fine for my HDMI displays at home. I even plugged it into my TV, and it stuck to the 100% scaling I picked for the othe

ERNOS: Erlang Networked Operating System

I've been reading Dreaming in Code lately, and I really like it. If you're not a dreamer, you may safely skip the rest of this post ;) In Chapter 10, "Engineers and Artists", Alan Kay, John Backus, and Jaron Lanier really got me thinking. I've also been thinking a lot about Minix 3 , Erlang , and the original Lisp machine . The ideas are beginning to synthesize into something cohesive--more than just the sum of their parts. Now, I'm sure that many of these ideas have already been envisioned within , LLVM , Microsoft's Singularity project, or in some other place that I haven't managed to discover or fully read, but I'm going to blog them anyway. Rather than wax philosophical, let me just dump out some ideas: Start with Minix 3. It's a new microkernel, and it's meant for real use, unlike the original Minix. "This new OS is extremely small, with the part that runs in kernel mode under 4000 lines of executable code.&quo

Haskell or Erlang?

I've coded in both Erlang and Haskell. Erlang is practical, efficient, and useful. It's got a wonderful niche in the distributed world, and it has some real success stories such as CouchDB and Haskell is elegant and beautiful. It's been successful in various programming language competitions. I have some experience in both, but I'm thinking it's time to really commit to learning one of them on a professional level. They both have good books out now, and it's probably time I read one of those books cover to cover. My question is which? Back in 2000, Perl had established a real niche for systems administration, CGI, and text processing. The syntax wasn't exactly beautiful (unless you're into that sort of thing), but it was popular and mature. Python hadn't really become popular, nor did it really have a strong niche (at least as far as I could see). I went with Python because of its elegance, but since then, I've coded both p