How to write dumber tests

Tests are hard.  The goal is to write a little bit of stuff that finds bugs in your code, you don't want to write unit tests so complex that they have bugs.  Charles (Luke) Lee breaks down some of the challenges, and gives solutions. Video from PyTexas 2014.

I have an entire rant about mocks, but that will wait for a later blog post.

How to write dumber tests

Beyond the For-Loop: Higher Order Functions and List Comprehensions in Python

My "Functional Programming with Python" talks were quite popular. Here's a brief introduction:

Beyond the For-Loop: Higher Order Functions and List Comprehensions in Python

preview: Python Library class

I'm developing a course on Python, and another on Professional Software development. Enclosed is a piece, showing the main basic modules in Python and why to use them.

best practices with Python's multiprocessing module

Thanks to dano and others on StackOverflow, I have more best practices for Python's multiprocessing module:

1) put everything in an if __name__=='__main__' block, vs having top-level code.  This is a Windows thing, but is good practice in general. Main-level code will be executed even if the module is imported, as opposed to being executed directly.

2) I'd previously been using signal.pause() to wait for subprocesses to exit and/or die.  Alas this has two challenges: a) this isn't available in Windows, and b) if a subproc dies, the parent will still hang around until explicitly killed/interrupted.

Here's an example of the right and wrong way to wait for a subproc.  If the signal.pause() path is enabled, then the program will run forever, ignoring the child proc that exits with an error.  The other path is more verbose, but correctly runs on Windows, and handles children correctly.

source

    import multiprocessing, signal, sys, time
    
    def wait_crash():
        time.sleep(1)
        sys.exit('crash')
    
    if __name__=='__main__':
        procs = [ multiprocessing.Process(target=wait_crash) ]
        for proc in procs:
            proc.start()
        if 0:
            signal.pause()              # XXX: not on Windows
        else:
            for proc in procs:
                proc.join()

output

    crash

slides: Tricky Linux Networking

slides: Tricky Linux Networking

talk: "Tricking out Linux kernel networking" tomorrow night

I'll be giving an excerpt of this talk tomorrow at Santa Monica Coloft -- please drop by!

Summary: "We are all familiar with classical TCP sockets. The Linux kernel gives us lots of other sockets, and internal services, to accomplish cool tricks with minimal effort."

The full thing will wind up to be around two hours, so this 20-30 min version will be less code and more jazz hands, which will make it fun!

http://www.meetup.com/LAHackers/events/198602002/

talk: Automatic Parameter Optimization

slides: http://johntellsall.com/class/auto-optimize/slides/index.html