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Book Review: Writing Idiomatic Python


Writing Idiomatic Python

Title: Writing Idiomatic Python

Author: Jeff Knupp

A small yet very useful book to teach you how to do things in a proper "Python way". It assumes you already know the language, and uses a very simple yet effective system of 1) describing the topic, 2) showing the harmful/wrong/typical way of doing it and 3) showing the idiomatic/best way to do it.

Comprehension lists, generators, choices of function arguments, default value caveats, even when to discard using objects in favor of simpler structures like named touples or just modules with functions.

Some of the examples were very revealing for me, as I come tainted from other object oriented languages and things are different in Python. You can read it in one or two afternoons so there's really no reason not to do it if you work with this programming language.


I updated my Python Gist with some notes from the book.

Recommended Articles - 2017/07/25

My latest bag of interesting articles and talks I've recently read, watched or listened too (you can check which podcasts I listen to here).

Emulators for Ubuntu Linux

I love videogames and I grow up with what now is called retrogaming. I also switched from Windows to Linux a while ago and, despite having a dedicated gaming desktop PC, it is mainly for recent titles. Taking advantage of some holidays I decided to setup some emulators at the laptop. It wasn't always easy so I decided to write this post, both for myself in case I need to repeat it and just in case it is of use to anybody else.

Shadow of the Beast - Commodore AMIGA

Note: At the time of writing this blog post, my system is an Ubuntu 16.04 x64. Based on my experience, Linux software is very sensitive to operating system versions (way more than Windows), so I can't guarantee that everything will run for example at Ubuntu 17.04.

For Arcade machines I use MAME, I use the oficial Ubuntu Software Center MAME Arcade build/binaries plus the GNOME Video Arcade GUI (available at Ubuntu Software Center too). The main issue is that it is a barebones GUI, missing many many features from things like MAMEUI, so I also keep MAMEUI inside a virtualized Windows XP SP3.

Before continuing, a small intermission to explain the reasoning behind that Windows XP virtual machine. VirtualBox has come a long way regarding Virtualization, and even under Linux (where I haven't been able to make work 3D emulation) it works quite nicely and I use it mainly for three tasks that have to do with videogames (among other unrelated tasks):

  • Playing old Windows games that don't work with Windows 7 and don't require Direct3D, like Civilization II.
  • Access advanced VirtualBoyAdvance features like object and map memory visualizers (GameBoy development related). It works really well inside VirtualBox, and Wine wouldn't load it.
  • Launching MAMEUI to see game snapshots (screenshots). Initially only until I finish doing the cleanup but I actually want to try running a virtualized MAME32. Note that I haven't tried running it with Wine, so it might work. From a host SSD it boots up in less than 3 seconds and just has configured a few shared folders to not need to move things in & out. And yes, XP is really old, but precisely is that version the one chosen for conflicting games (with Vista and 7 more than a few old Windows games stopped working). Oh, and for USB 2.0/3.0 and other goodies support, install also the VirtualBox Extension Pack.

For old Nintendo systems (Gameboy, GameBoy Color, Gameboy Advance, NES/Famicon and SuperNintendo/SuperFamicon) I use Higan. You have recent versions at PlayDeb2, but wherever you grab it, should at least be v103. The main reason (apart from typical better emulation and speed) is that GameBoyAdvance BIOS ROM loading was mostly broken under Linux and got fixed around version v100. One remark, to run GameBoy Advance ROMs, you need the BIOS ROM.

To play the SEGA MegaDrive/Genesis, I used DGen/SDL, but you need to compile it and it is command-line based, so in the end I tried and am happy with Gens, which can be obtained at PlayDeb2.

My beloved Commodore AMIGA 500 still works nicely, but floppy disk loading times and the like are tiring, so I also play this great computer via emulation. Especifically, using FS-UAE + FS-UAE Launcher. A few notes/tips also here:

  • RTFM. There are many options and some "flows" are really clunky, like disk swapping (you need to "multi-select" all disks to be able to F12 and switch them, but the UI doesn't mentions this anywhere). The documentation is almost a mandatory read in this case
  • To run anything you need the desired AMIGA firmwares (e.g. I needed Amiga 500 one). In this case there are even official commercial compilations of AMIGA software which include them
  • To run Workbench tools you need AMIGA Workbench, and to run hard disk programs you need to first create an AMIGA hard drive (via the configuration)
  • Combining that the AMIGA was prone to give Guru meditation errors either with cheats or with obscure unrecoverable errors, plus other mysterious hangups that make my whole Ubuntu freeze to death once or twice while running in fullscreen, this is the only emulator that didn't felt 100% stable. Still, in general works nicely and I'm not entirely sure it is not due to my graphics card, as in windowed or borderless maximized window I had no such issues.

And finally, to play old MS-DOS games either not available at Good Old Games or that I already own, nothing beats the great DOSBox, which can for example be found at Ubuntu Software Center. This is a generic operating system virtualization so each game might need individual tweaks, but many work perfectly out of the box.

One thing that I haven't tried yet is Playstation/PSX emulation. PS2 is still not 100% emulated under Windows so I don't even care, but I have pending to check for Linux PSX emulators, there should be something decent already...

Once setup, all this software works nicely, but it is not an easy task (at least not without this post summarizing it ;). There is a great all-in-one solution that I tried, RetroArch. It is a multi-emulator GUI-software-thingy that supports plugins to run many many systems, from legacy ones to really recent stuff like Wii's Dolphin emu. The reason I wasn't convinced by it is that at least when I tried it a few months ago, the Linux build was unstable and only worked with some systems. Windows build looked way more robust (I tested it) but as wasn't my plan uninstalled. It is the base system used at the RetroPie distribution, so the distro is correctly setup and already contains many basic features I probably missed out, but it wasn't as trivial as I thought.

My laptop is an old 2012 Dell XPS but runs perfectly the systems mentioned above. I know a Raspberry Pi can even run now Neo-Geo games at a decent framerate so one day I'll get one, but my two main reasons for waiting are a) I wanted to do this learning experience before grabbing a quick'n easy solution, and b) I still want to wait a bit further until commodity hardware evolves and runs more powerful machines like the PSX or GBA without frame skipping (probably something like a Raspberry pi 4 will do).

Hope this list helped you out!

On Python 3, Flake8 and mypy

This is a small post just to write about what we use at work and what I'm starting to use at home too for personal experiments. I thought would be interesting to share as at least two friends showed interest about the topic.

First, we're using Python 3.6. I've been using Python for around a year and a half only, and I have almost fully skipped python 2.x, so I am not biased with the "2 is better, don't migrate to 3!" war. I just like a lot all the new features and the way better encoding handling so my ignorance makes me not understand why would people keep with an old and worse version... ¯\(ツ)

Then, we use flake8 as our linter, with every restriction on except the line size rule (which we've upped to a more reasonable 120 characters). But as some people have tendency to drift away from coding standards, to make sure everybody follows it my colleages have setup an integration test that uses flake8.api.legacy to run the checks and make sure there are no violations. It can look silly sometimes, but helps a lot to maintain a uniform codebase.

And finally, again thanks to my colleages we're doing typed Python using mypy. It adds optional type checking both to Python 2 and 3 and provides a linter-check call which reports any error (so can be actually made mandatory). Added to the same battery than the normal linter test, it means all new code must be fully typed or you won't be able to push a build. It is quite robust and you have typing hints for everything, from basic types to optional parameters, callable function handlers, generics and multiple return values (Union type, you still need to specify to it which values are allowed). It stings a bit when you begin using it but after a while it's so nice to forget about weak typing errors (one of my main complaints of scripted languages).

I highly recommend you to watch this PyCon 2017 talk of the creators of mypy to both see it in action and learn about its internals:

All of this combined with some decent tests (kind-of-TDD-without-being-always-strict) means I can do non-trivial changes and refactors without worrying of breaking unexpected things. If you do python, you should try too, the absence of fear makes you feel really nice.

The truth

Oh, and just in case you want to check it out, I keep a small gist where I from time to time write notes and miscellaneous things regarding Python that I learn and wish to keep for the future.

As a tiny sample, I wrote a Python implementation of a double linked list that you can check at my GitHub. It has both flake8 and mypy "linter tests" that check the code for errors or missing typings. Sadly, variable type hinting is only available from Python 3.6 onwards so I've used comment annotations at two places I needed to, as I'm for now using Python 3.5.

And finally, if your IDE is Sublime Text as it is mine, I wrote a post about installing a few linters on the application to directly code clean and best-practices approved Python.

UPDATE #1: Added Youtube talk video.

UPDATE #2: Added my double linked list example.

UPDATE #3: Added link to my post about Sublime Text Python linters.

Recommended Articles - 2017/06/12

Latest bunch of posts, articles and links I found out interesting.

And, while not news, I also wanted to mention (as I'm recommending to my friends) anybody to do the following (free) Coursera course: Learning How to Learn: Powerful mental tools to help you master tough subjects. It is from the University of California and, despite being a 4 weeks course, you can do it more or less in half the time (if you have enough spare time). It not only teaches you how your brain works but really provides good tips to improve your learning lessons. I really enjoyed it and highly recommend it. I'll probably mention other online courses when I finish them.

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