2012-08-25 14:24

Qt Mac Tips

My team has been working on porting some PyQt stuff to Mac OSX, and we have run into several Qt bugs, sadly. Here are two, and the workarounds we found.

Native dialogs are broken.

Using QFileDialog.getExistingDirectory we noticed the following symptoms:

  • If you do nothing, the dialog went away on its own after about 20 seconds.
  • After you used it once, it may pop up and disappear immediately. Or not.

Solution: use the DontUseNativeDialog option.

Widgets in QTreeWidgetItems don't scroll.

When you use Widgets inside the items of a QTreeWidget (which I know, is not a common case, but hey, it happens), the widgets don't scroll with the items.

Solution: use the -graphicssystem raster options. You can even inject them into argv if the platform is darwin.

2012-08-20 22:31

Istanbul, The Lost Pictures


I will probably never take a better picture than this one.

I found a camera today at home, and then it hit me: this was the camera we took to Istanbul, dropped on the floor, never worked again, and I never found after we came back! And it still had the SD card in it!

So, here are the pictures (not even filtered), so family can see them.

2012-08-17 22:45

Cloud Atlas

I am not going to explain this book. It's enough, I think, to say I loved it, and that it's strange, and that it's a bit of a mistery.

Imagining a universe in which all the contents of the book could be real at the same time in a way that would allow all the pieces to be written as they are and yet, be, somehow, not the novel they are, but a found artifact, is both depressing and ellusive.

At the end, I felt something I can only describe as retrospective hope, the feeling that things were supposed to end up better, but that even as terribly as they did end, were it not by that earlier hope, they would have been more grim.

The control the author has over his own style is impressive. This book feels written by half a dozen completely different writers.

Some quotes (which may only make sense once you read the book):

"The sun was deaf'nin' so high up, yay, it roared an' time streamed from it."

"In the first set, each solo is interrupted by its successor: in the second, each interruption is recontinued, in order. Revolutionary or gimmicky? Shan't know until it's finished, and by then it'll be too late"

"What wouldn't I give now for a never-changing map of the ever-constant ineffable? To posess, as it were, an atlas of clouds."

2012-08-17 10:10

Nikola 4 Released


  • Previous/Next post links
  • Teaser support
  • Support posts with HTML "sources"
  • Site checking script (nikola_check)
  • Maximum image size in galleries
  • Image descriptions in galleries
  • Image exclusion in galleries
  • Special "draft" tag
  • Pretty code listings ("code galleries")
  • Page descriptions
  • Easy theme tuning via Bootswatch
  • Support for WebAssets bundles
  • "Filters" for powerful file post-processing


  • Improved HTML output
  • Support multiple time formats in post metadata
  • Slugify tag names for URLs
  • Archive path and filename configurable
  • Galleries sorted by date (supports EXIF)
  • Rotate gallery thumbnails (EXIF)
  • Tag feeds in tag pages
  • Colorbox support in restructured text figures
  • Fix for content displaying too wide
  • Changelog

As usual, you can discuss bugs or make feature requests at the nikola-discuss group and I love to know of sites using Nikola.

Hope you like it!

2012-08-13 17:12

Trying out CloudFlare

It's not that I need a CDN in any way, since the traffic for this site is little and the way the site is built is light, but hey, it's free, easy to setup and easy to leave when I feel like it. And I expect to have significantly higher traffic eventually after I finish some not-so-secret projects.

What's CloudFlare's service? They take over your DNS, then put a reverse proxy between your site and the clients. That reverse proxy then uses a CDN to serve you the pages from a conveniently located server, and can rewrite the HTML/JS/CSS in some ways to make it faster/safer/nicer.

It also supposedly will protect my site from different kinds of attack (the only one that could possibly affect me was DOS attack, but thanks anyway ;-)

Also, they offer a platform so apps can provide services for me, like intruder detection, analytics, and others, which is a very cool idea.

So, I created an account at cloudflare.com and configured it so that //ralsina.me (which is this exact same site except for wrong comment counts) is served via cloudflare, and ralsina.me is served directly.

What I've seen so far:

  • Setup is very simple
  • It works, even setting up experimental features
  • It does seem very slightly faster, but that's not a surprise since the tiny server the site runs on has good conectivity and ample unused resources.
  • It does do a good job of automatically optimizing some things in ways that are generally accepted as a good idea (in other words, my pingdom and YSlow numbers moved up)

So: no pain, maybe some gain. I will probably move all sites into it tonight.

2012-08-11 15:33

Sometimes More is More

We all hear all the time that less is more. That simple is better, that complex is worse, that options are evil, that defaults are what matter.

And yes, that is about 90% true. Except when it is false, which I know because I bought a coat a few weeks ago.

This is a rather nice coat, and if you saw it without much care you would miss one of its best features: it has two pockets on each side.

Let's think about why we want pockets in the sides of coats:

  1. To put our hands when it's cold. Since this is a cold weather coat, that's important. In moderate climates like this one, gloves are more trouble than they are worth, and just sticking hands in pockets is enough.
  2. To put stuff that is not hands in them: keys, phones, money, candy, etc.

For the first use case, we want the pockets to be shallow angled, so that the hand goes in naturally, almost horizontally. Also, we want the access to be unobstructed, so no zippers, which also scratch the wrists.

For the second use case, we want things not to fall off. So we want either a vertical pocket (perhaps with a flap) or a zipper. Zippers suck because you can forget to zip them, and things fall off. Vertical pockets are awful to put your hands in.

So, my jacket has two pockets on each side, one with a zipper, one without. One for hands, one for things. Since it's a thick coat you don't see it unless you know what you are looking for, and it's trivial to use: everything goes in the zipped one, except my hand. I can even check the contents of the zipped pocket without getting my hands out of their pockets.

This is one case where more is more, complex is better, options are awesome, and defaults don't matter. Now, if you find a place in software where that's the case, that's an opportunity.

2012-08-10 20:06

Nikola: Filters & Bundles


Filters let you postprocess your output. Think of it like instagram for websites, but useful. You can configure per file extension a series of python functions or shell commands, which will be applied in place to the output file.

For example, suppose you want to apply yui-compressor to your CSS and JS files:

    ".css": [filters.yui_compressor],
    ".js": [filters.yui_compressor],

There, filters.yui_compressor is a simple wrapper around the command so that it applies in-place to the output files.

If you use strings there (untested), they are taken as commands. The "%s" will be replaced by the filename, the usual crazy shell quoting rules apply:

    ".jpg": ["jpegoptim '%s'"],
    ".png": ["pngoptim '%s'"],

Keep in mind that the filters modify the output of Nikola, not the input, so your images, CSS, and JS files will not be touched in any way. And of course changing the filters applied to a file will force a rebuild, so you can experiment freely.


Having many separate CSS or JS files is usually a nono for performance reasons because each one may involve a separate HTTP transaction. The solution is to "bundle" those files in a single, larger file.

The reason not to do that is that usually it means having a huge, uncomfortable thing to handle. So Nikola tries to give you the best of both worlds, by letting you have separate files, and bundling them (or not) on build.

There is a new option, USE_BUNDLES that defaults to False, and there are some changes in the theme templates so that it uses the bundled version when needed.

This was only possible thanks to Webassets. However, if you don't have Webassets installed, or you don't enable USE_BUNDLES, this should cause no changes in the output.


These new features will allow Nikola users to improve their site's performance with minimal tweaking, which is always a good thing.

2012-08-07 16:17

The Minimal Server

I was a sysadmin for a long time. I did that for money, so I never really wanted to spend time doing the same thing in my own time, which lead to a severe case of cobbler's children walking barefoot in my private server.

So, today at lunch, I decided to clean up my garbage. So this is what I ended up with, which is the minimal server that is good enough to be generally useful for me.


This is a cheap VPS provided by the nice folks at burst.net who are not giving me anything to speak nice things about their service. However, I will do it anyway:

  • Crazy cheap ($5.50 but I have a 20% discount for life)
  • Good amount of monthly bandwidth
  • Lots of disk space
  • Good uptime
  • Fast network
  • Very cheap
  • Decent performance


I had CentOS 5 installed, and it stays. If burst ever starts offering Ubuntu Precise, I may switch. Or, since this works, I may not.

What's good about CentOS? It's stable and boring.

What's bad about CentOS? It's too boring. Lots of cool stuff just isn't packaged.

Web Server

I need to serve a bunch of domains, but I have a peculiarity: they are all static sites. I want:

  • Low resource usage
  • Decent performance (that mostly involves supporting ranges and content negotiation)
  • Stable
  • Support directory indexes
  • Easy configuration
  • Virtual domains by name

Almost any server works well for this. Even Apache, except for the easy configuration bit. I ended up with gatling because it fits those criteria fairly well.

  • It uses about 1.4MB of RAM , which is always nice in a VPS
  • It's pretty fast
  • Has not crashed in 2 hours?
  • Supports indexes
  • Here's the configuration: "-c /srv/www -P 2M -d -v -p 80 -F -S" (yes, there is no config file at all)
  • Virtual domains are just folders and symlinks inside /srv/www which is the easiest possilble way to do it.
  • It supports reverse proxying for when I want to try a python web app I am working on.

Mail Server

No, I don't want a mail server. I have gmail and/or a real mail server for that. I want to get the mails from cron. For this, I used ssmtp and an extra gmail account. It works, and here's the whole config:

[email protected]
[email protected]

The best I can say about this configuration is that it works, and doesn't involve running a daemon.


For when I need to be in two places at the same time: OpenVPN rules, and there is no argument. I have a squid running occasionally, and there is a Quassel core for IRC stuff. I installed mosh to make ssh less painful, rsync handles file deployment and backup storage, cron schedules stuff, and that's it.


Plenty of free RAM and CPU (yes, that's the full process list):

[[email protected] ~]# ps aux
root         1  0.0  0.1   2156   664 ?        Ss   22:01   0:00 init [3]
root      1135  0.0  0.1   2260   576 ?        S<s  22:01   0:00 /sbin/udevd -d
root      1518  0.0  0.1   1812   572 ?        Ss   22:01   0:00 syslogd -m 0
root      1594  0.0  0.1   7240  1032 ?        Ss   22:01   0:00 /usr/sbin/sshd
root      1602  0.0  0.2   4492  1112 ?        Ss   22:01   0:00 crond
root      1630  0.0  0.1   5684   716 ?        Ss   22:01   0:00 /usr/sbin/saslauthd -m /var/run/saslauthd -a pam -n 2
root      1631  0.0  0.0   5684   444 ?        S    22:01   0:00 /usr/sbin/saslauthd -m /var/run/saslauthd -a pam -n 2
root      1636  0.0  0.2   3852  1372 ?        S    22:01   0:01 /opt/diet/bin/gatling -c /srv/www -P 2M -d -v -p 80 -F -S
root      1677  0.0  0.2   4284  1232 ?        Ss   22:02   0:00 SCREEN /root/quasselcore-static-0.7.1
root      1678  0.0  2.1  36688 11148 pts/0    Ssl+ 22:02   0:03 /root/quasselcore-static-0.7.1
root      3228  1.0  0.7  12916  4196 ?        Ss   23:28   0:13 mosh-server new -s -c 8
root      3229  0.0  0.3   3848  1588 pts/2    Ss   23:28   0:00 -bash
root      3275  0.0  0.1   2532   908 pts/2    R+   23:48   0:00 ps aux
[[email protected] ~]# w
 23:49:03 up  1:47,  1 user,  load average: 0.00, 0.01, 0.00
USER     TTY      FROM              [email protected]   IDLE   JCPU   PCPU WHAT
root     pts/2   23:28    0.00s  0.01s  0.00s w
[[email protected] ~]# free
             total       used       free     shared    buffers     cached
Mem:        524800      49100     475700          0          0          0
-/+ buffers/cache:      49100     475700
Swap:            0          0          0

All things considered, fairly happy with the result.

2012-07-26 16:57

Christians say the funniest things!

I have promised not to be a troll (anymore) so I will try to answer in a sensible manner.

Here's the article I am replying to go read it if you want. I will not reply to all of it, but will instead cherrypick a couple of paragraphs.

In response to the "forcing dogma" panel:

So... religion is fine, unless you actually believe in it? Should parents not pass their political, ethical or moral views on to their children as well? What parts of parenting would be left if parents were to avoid passing their views on to their kids? The irony here is that silence is itself a statement. Avoiding any mention of God to your kids sends as clear a message as talking about God: specifically, it tells your kids that God's existence is either untrue, unknown, or unimportant. Because if you knew Him to exist, surely you'd share that knowledge, right?

Let's start from the top: you don't know god exists. You have faith that he exists, but you don't know it for a fact. If you knew for a fact that he exists, you could not possibly have faith because faith excludes certainty. As your bible says, faith is "the substance of things hoped for, the evidence of things not seen."

So, do I tell my son god doesn't exist? Nope. I tell him I think he doesn't exist, and that I have never seen r heard of any reliable evidence or datum that points towards his existence, but also that some people do believe he does exist. I told him that because I feel that's a honest answer. If your honest answer is "god exists", then bully for you, but from the point of view of a non-believer you are telling your son a lie, or at best a half-truth. And if you really don't know he exists for a fact then you are just lying.

Now, are you sayin that you know god exists factually? Based on what? That's the usual slippery slope for this argument. The religious are the ones making statements of fact based on tradition. To the rest of us, they just seem to be playing loose with what "fact" means, or what "god" means or what "know" means.

So, no, don't avoid mentions of god, just avoid lying to your kids if you can.

This next section is probably the worst, because it's just an incoherent argument. A kid asks, “Dad, what happens to us after we die?” The author compares providing the Christian answer to this question with correcting your kid for having green as a favorite color. What?? That just isn’t a coherent argument. In what world are those two ideas parallel, or even comparable?

According to the webcomic, good parenting is to pretend to be agnostic, and say that “no one really knows for sure.” Of course, if the Resurrection is true, that claim is false. So to be a good parent, you apparently have to deny the Resurrection and embrace agnosticism, treating beliefs about the afterlife as mere matters of personal preference like having a favorite color. This is just… stupid. There’s just no other way of describing it. Imagine if we treated everything that way. “Dad, what’s 3 x 3?” “No one really knows for sure. What do YOU think 3 x 3 is?”

So, comparing life after death with color preference is stupid and incoherent, but comparing it the christian belief of resurrection with basic arithmethics is a-ok? That must have taken some effort to write with a straight face, I'm sure.

So, let's go slowly on this one. Beliefs about the afterlife are, like most other beliefs, probably not a personal preference, but just something you have, because of, in most cases, indoctrination early in life, peer pressure, and just because you live in a society where that belief is normal and approved of.

But what is it your belief in the afterlife is not?

  • It's not inherent to "you". If you were born in another place or time, you would probably believe something else.
  • It's not undisputed. Because there exists a majority of people who don't believe the same thing, either by details or entirely.
  • It's not unique. Because other religions have had similar resurrection beliefs.
  • It's not reliable. Even if we were to accept everything the bible says as true that would not mean we know what will happen to you or to me after we die. We would have a testimony about what happened in a few days in the afterlife of a specific person, at a point in the past, as told to someone by someone. Is that the same as knowing what will happen? No it's not.

Let's compare that to 3x3 as the author attempted:

  • If I was a chinese in the 12th century: 3x3 is 9.
  • There is no group of people that believes 3x3 is 8 or 10.
  • There has not been in the past any real disagreement about the value of 3x3. We have not achieved that result via a gradual improvement.
  • We rely on 3x3 being 9 every day in our lives. If you drive a car, use a phone, or zip your pants, you are agreeing 3x3 is 9.
  • We don't expect 3x3 not to be 9 in the future.

Notice any differences? Yes, me too.

Personally, I consider your faith in god more akin my liking Queen (the band, not the ruler). I was exposed to Queen at the right time, it was approved by my peers, and I like it. On the other hand, I understand that Queen is not everyone's cup of tea, and I don't claim Queen to be the "right" band.

The whole "if the Resurrection is true, that claim is false" line of thought is not logical. If my cat had wings, then the claim that winged cats are awesome is false. But my cat doesn't have wings. Does it make the winged cats less or more awesome that he doesn't? It's not that it's not right, it's that it's not even wrong.

Also, Oatmeal, shame on you about Galileo, really, look it up ;-)

2012-07-25 22:25

Driving a Nail With a Shoe I: Do-Sheet

I had proposed a talk for PyCon Argentina called "Driving 3 Nails with a Shoe". I know, the title is silly, but the idea was showing how to do things using the wrong tool, intentionally. Why? Because:

  1. It makes you think different
  2. It's fun

The bad side is, of course, that this talk's contents have to be a secret, or else the fun is spoiled for everyone. Since the review process for PyConAr talks is public, there was no way to explain what this was about.

And since that means the reviewers basically have to take my word for this being a good thing to have at a conference, which is unfair, I deleted the proposal. The good (maybe) news is that now everyone will see what those ideas I had were about. And here is nail number 1: Writing a spreadsheet using doit.

This is not my first "spreadsheet". It all started a long, long time ago with a famous recipe by Raymond Hettinger which I used again and again and again (I may even be missing some post there).

Since I have been using doit for Nikola I am impressed by the power it gives you. In short, doit lets you create tasks, and those tasks can depend on other tasks, and operate on data, and provide results for other tasks, etc.

See where this is going?

So, here's the code, with explanations:

cells is our spreadsheet. You can put anything there, just always use "cellname=formula" format, and the formula must be valid Python, ok?

from tokenize import generate_tokens

cells = ["A1=A3+A2", "A2=2", "A3=4"]
values = {}

task_calculate creates a task for each cell, called calculate:CELLNAME. The "action" to be performed by that task is evaluating the formula. But in order to do that successfully, we need to know what other cells have to be evaluated first!

This is implemented using doit's calculated dependencies by asking doit to run the task "get_dep:FORMULA" for this cell's formula.

def evaluate(name, formula):
    value = eval(formula, values)
    values[name] = value
    print "%s = %s" % (name, value)

def task_calculate():
    for cell in cells:
        name, formula = cell.split('=')
        yield {
            'calc_dep': ['get_dep:%s' % formula],
            'actions': [(evaluate, (name, formula))],

For example, in our test sheet, A1 depends on A3 and A2 but those depend on no other cells. To figure this out, I will use the tokenize module, and just remember what things are "names". More sophisticated approaches exist.

The task_get_dep function is a doit task that will create a task called "get_dep:CELLNAME" for every cell name in cells.

What get_dep returns is a list of doit tasks. For our A1 cell, that would be ["calculate:A2", "calculate:A3"] meaning that to calculate A1 you need to perform those tasks first.

def get_dep(formula):
    """Given a formula, return the names of the cells referenced."""
    deps = {}
        for token in generate_tokens([formula].pop):
            if token[0] == 1:  # A variable
                deps[token[1]] = None
    except IndexError:
        # It's ok
    return {
        'result_dep': ['calculate:%s' % key for key in deps.keys()]

def task_get_dep():
    for cell in cells:
        name, formula = cell.split('=')
        yield {
            'name': formula,
            'actions': [(get_dep, (formula,))],

And that's it. Let's see it in action. You can get your own copy here and try it out by installing doit, editing cells and then running it like this:

[email protected]:~/dosheet$ doit -v2 calculate:A3
.  get_dep:4
.  calculate:A3
A3 = 4
[email protected]:~/dosheet$ doit -v2 calculate:A2
.  get_dep:2
.  calculate:A2
A2 = 2
[email protected]:~/dosheet$ doit -v2 calculate:A1
.  get_dep:A3+A2
{'A3': None, 'A2': None}
.  get_dep:4
.  calculate:A3
A3 = 4
.  get_dep:2
.  calculate:A2
A2 = 2
.  calculate:A1
A1 = 6

As you can see, it always does the minimum amount of effort to calculate the desired result. If you are so inclined, there are some things that could be improved, and I am leaving as exercise for the reader, for example:

  1. Use uptodate to avoid recalculating dependencies.
  2. Get rid of the global values and use doit's computed values instead.

Here is the full listing, enjoy!

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