Posts about python (old posts, page 30)

2010-02-23 12:03

Preview chapter of "Grok 1.0 Web Development"

The nice fellows at Packt Publishing have sent me a copy of Grok 1.0 Web Development by Carlos de la Guardia to review.

I am reading it and expect to write about it in a few days (BTW: nice so far! My proposed slogan: it's like zope, without the Java [1]), and here is a sample chapter so you can see what it's about. It's easy to read standalone, too:

Chapter 5: Forms

Having had to deal this week with the brokenness that's Django oldforms (legacy site, don't even ask), the Grok way of dealing with forms is refreshing ;-)

[1] Yes, of course I know Zope had no Java in it, it just felt like Java ;-)

2010-02-22 00:54

Are we really this clueless about software costs?

Here's what Ohloh has to say about the cost of developing Marave

Really, Marave is maybe a month of part-time programming. How could that possible be U$S71355, or "1 Person Years"?

Is this garbage the best we have to estimate costs? If that's the case, then whenever you see something about "Open source program X would take Y years and cost Z dollars to write", cut it down by a factor of 10 or more.

Here's what Marave really costed to develop:

  • Nothing.

Ok, here's what it would have costed if I had charged for it:

I am guessing about 100 hours of my time. At my "I hope they pay me this much" rate of U$S 40/hour , that's U$S 4000, which means Ohloh is off by 1600%.

OTOH, for that much freelance work I would not charge you the full rate, I would probably end charging you more like U$S20/hour which would make Ohloh's guess over 3000% too high.

In conclusion: if you like my code (and hey, you can see it for yourself), hire me, I am incredibly cheap, or amazingly fast!

2010-02-21 21:49

Marave 0.6 is out

Version 0.6 of Marave, my peaceful, fullscreen text editor is now available at the usual place:

New stuff:

  • Syntax highlighter
  • Plugins
  • Bugs fixed
  • Nicer animations
  • Code cleanup

Gratuitous screenshot:

2010-02-19 22:07

The aha! moment

I had a small task today in Marave. The goal was:

  1. Fade in a widget
  2. Set a variable
  3. Fade in another one

It's important that things are done in that order and it's also important that the app remains interactive.

And here's the code to do that (simplified):

def fadein(thing, target=1., thendo=None):
    * thing is a QWidget
    * thing.proxy is a QGraphicsWidget
    * thendo is callable
    * target is the desired opacity

    thing.anim=QtCore.QPropertyAnimation(thing.proxy, "opacity")
    if thendo:

And this is how you use it:

def later():

fadein(widget1, thendo=later)

Isn't that lovely? Having functions as first class objects means I can just take later as a closure, along with widget2 and avar, which need only be defined in the local scope, and the call chain will work just as I wanted!

Yes, many other languages can do this, and in Javascript it's one of the most common tricks, but consider that PyQt is a wrapper for a C++ library!

I think this kind of usage shows the real added value PyQt brings to the table, it's not just that python avoids the boring compiles, or that you have the awesome standard library to use, but that the language itself enables you to do things that are not practical in C++.

In C++ the only way I can think of is creating a slot that's the equivalent of later, then chaining the signals... which means that this throwaway later becomes part of the interface of a class!

I would have to define later somewhere else on the file, separate from its only usage (maybe even inlined in the header file).

Even then, that's not equivalent: avalue may be something that was only avalable before the first call to fadein, (for example, the time of the first fadein): I would have to create a place to store it, make it reachable by later... and wht happens if you try to do this again while the first fadein is in progress?... it gets hairy.

Programming is like a slap in the face sometimes... you realize that things you use without even noticing are far from trivial.

So, remember young padawan: you can choose you tools. Choose wisely.

2010-02-18 18:50

Extending Marave

Marave is a text editor. If there's one thing that's true of most text editors, it's this: they lack the exact features you need.

So, the solution, in the ancient tradition of Emacs and Vim is... make it extensible.

I am a big fan of programs that can be extended by users.

So... here's the anatomy of a Marave plugin as it stands right now on SVN trunk, which of course can change any minute.

Creating a plugin

You just need to create a .py file in the plugins folder.

Here's the most basic plugin, which does nothing:

# -*- coding: utf-8 -*-

from plugins import Plugin
class Smarty(Plugin):
    description='Smart quote and dash replacement'

Default values for anything configurable (in this case, "mode") is just added to the class.

The mandatory fields:

  • shortcut: a keyboard shortcut that triggers this plugin
  • name: a short name
  • description: a one-line description of what it does

What does it do? It adds the plugin to the plugin list in the prefs dialog, and you can open its configuration dialog, where you can change the shortcut:


If you enable this plugin, whenever the shortcut is used the "run" method of the plugin is called.

Making the Plugin Configurable

This plugin supports different modes of operation. To make this reachable to the user, you need to implement a few extra methods.

The addConfigWidgets method takes a dialog argument and adds whatever you want there:

def addConfigWidgets(self, dialog):
    print 'Adding widgets to smarty config'
    self.q=QtGui.QCheckBox('Replace normal quotes'))
    if 'q' in self.mode:
    self.b=QtGui.QCheckBox('Replace backtick-style quotes (` and ``)'))
    if 'B' in self.mode:
    self.d=QtGui.QCheckBox('Replace -- by en-dash, --- by em-dash'))
    if 'd' in self.mode:
    self.e=QtGui.QCheckBox('Replace ellipses'))
    if 'e' in self.mode:

And then the config dialog will look like this:


But then you need to save those options somewhere, which you do reimplementing saveConfig:

def saveConfig(self, dialog):

    self.settings.setValue('plugin-''-shortcut', self.shortcut)

    if self.q.isChecked():
    if self.b.isChecked():
    if self.d.isChecked():
    if self.e.isChecked():


And you need to load those settings and put them in your class, too:

def loadConfig(self):
    print 'SMARTY loadconfig', self.settings
    if self.settings:
        if sc.isValid():
        if mode.isValid():

Making it Work

And yes, you need to make it do something useful. The plugin has access to a "client" which is Marave's main window. Everything is available there, somewhere ;-)

def run(self):
    print 'running smarty plugin'
    prog=QtGui.QProgressDialog("Applying smarty"),
    for i,l in enumerate(text):

And there it is, if you enable the smarty plugin, you can "fix" your quotes, dashes and ellipsis with a key combination :-)

Full source code here:

Still to be done: other ways to integrate plugins into the UI, buttons, panels, etc.

2010-02-16 19:20

Yak Shavings for February 16, 2010

yak shaving
(idiomatic) Any apparently useless activity which, by allowing you to overcome intermediate difficulties, allows you to solve a larger problem.

A while ago, I wrote how I implemented a generic syntax highlighter for PyQt using Pygments.

I got a request for such a feature in Marave, so I digged that code and... it's freaking useless. It's just too slow for reasonable use.

So, that yak's hair is all grown up again, and I just got this new pair of scissors!

The goal is a way to highlight syntax in a QPlainTextEdit that:

  • Doesn't require programming to add a new highlighter
  • Doesn't require programming to add a new color scheme
  • Doesn't require me to spend a year writing highlighters for existing languages
  • Is fast enough

A quick google shows that for C++ you can use Source highlight qt which is based on GNU source highlight.

Alas, no python binding that I could find. So, let's write one!

Here it is:

And here's a screenshot of the demo program running, showing itself in its entirety:

You can create a color scheme using CSS, a language definition is a text file, there are a bazillion already written, it seems to be fast enough.

So, another yak shaved, another feature (not finished!) for Marave

2010-02-15 18:47

How to implement "replace all" in a QPlainTextEdit

This is not interesting for almost noone, but since my google-fu didn't let me find it and it was a bit of a pain to do:

This is how you implement 'replace all' in a QPlainTextEdit (or a QTextEdit, for that matter) using PyQt (similar for C++ of course).

def doReplaceAll(self):
    # Replace all occurences without interaction

    # Here I am just getting the replacement data
    # from my UI so it will be different for you

    # Beginning of undo block

    # Use flags for case match
    if self.searchReplaceWidget.ui.matchCase.isChecked():

    # Replace all we can
    while True:
        # self.editor is the QPlainTextEdit
        if r:
            if qc.hasSelection():

    # Mark end of undo block

There are other, easier ways to do it, but this one makes it all appear as a single operation in the undo stack and all that.

2010-02-12 22:25

Marave 0.5 is out!

Just uploaded Marave 0.5 to the usual place. Marave is a relaxed, fullscreen text editor that tries not to distract you.

It even includes a simple music player just so you don't have to think about switching to another application!

This release has several bugs fixed, and looks a bit nicer.

The main new feature is ... internationalizacion. It now includes a spanish translation only, but if you want to help translating it to any other language, please step forward!

There are only 60 phrases to translate, so it shouldn't be more than one hour of work.

Here's a screenshot of this release:


Marave is free software under the GPLv2, and should work on any platform where PyQt works, which means Windows, Mac, and Unix-like operating systems, at least.

2010-02-11 14:00

Packaging and shipping is HARD

I have worked really hard on Marave, a full screen editor in the style of ommwriter, DarkRoom, WriteRoom, pyRoom, etc. I have worked very hard and I want users to use it.

Or not even that, I want them to have a chance of using it.

That means I want it to work on Windows (and maybe OSX some day, too, if someone helps me). Which means, I have to pakage it for windows.

Let's do a quick comparison here from the points of view of the user and the developer.

The User, In Linux

This is in Arch Linux, which is what I use, in other Linux variants it will be pretty much the same once Marave is a bit more well known.

yaourt -S marave-svn --noconfirm

That gets the code from SVN (right now it's the best way, later I will package releases, too), all required dependencies, builds and installs. It takes all of 15 seconds in my notebook.

After that, you have a fully working Marave.

In case it's not packaged for your distro, just install PyQt (which surely is) and run this command:

easy_install marave

The User, in Windows

You go to, click on "Marave-0.5.win32.exe" (Not linked yet, it's not finished), then download a 10MB program. That is a 10MB program because windows doesn't believe in packages and dependencies. On Linux, a Marave package could be under 1MB (most of it images), and not be executable, just data.

Of course nowadays web browsers don't actually run programs on download, so... let's see it as a gallery!


Yes, save it.


Double click to open it


Yes, I agree


Sure, whatever




Good to hear!

Now, this Marave that just got installed may or may not currently work because of a missing MSVCR90.DLL but that's for the next section...

The Developer, in Linux

First, here's the biggest problem a Linux packager can have:

Since Marave is a new app, and I develop it in the rather cutting-edge Arch Linux, it uses some newish features only available in recent versions of Qt. In fact, it doesn't work with PyQt < 4.6, which is not available in some slow distros, like Debian, or even in a not-latest Ubuntu.

Solution? Well, I could just ignore it, but what the heck, let's fix it instead!

Thanks to PyInstaller it's not even hard to do, here's the spec file:

a = Analysis([os.path.join(HOMEPATH,'support/'), os.path.join(HOMEPATH,'support/'), 'marave/'],

pyz = PYZ(a.pure)
exe = EXE(pyz,
        name=os.path.join('build/pyi.linux2/main', 'marave.exe'),
        console=0 )

coll = COLLECT( exe,
            name=os.path.join('dist', 'marave'))

Use this, and PyInstaller will produce a nice folder full of everything Marave needs to run on any Linux.

OTOH, if you can rely on a recent PyQt being available, it's also simple. Here's a packaging configuration for a similar package in Arch Linux (I must confess not having done one for Marave yet). For other distributions it should be about as simple, if more verbose, and someone else probably does it for you:

# Contributor: Roberto Alsina <[email protected]>
pkgdesc="Create PDFs from simple text markup, no LaTeX required."
arch=('i686' 'x86_64')
depends=('python' 'setuptools' 'docutils' 'pygments' 'python-reportlab' 'python-simplejson' 'pil')
source=($pkgver.tar.gz LICENSE.txt)
optdepends=('uniconvertor: vector images support'
            'python-svglib: SVG support'
            'python-wordaxe: hyphenation'
            'pythonmagick: PDF images support')
build() {
cd $startdir/src/rst2pdf-$pkgver
python install --root=$startdir/pkg || return 1
install -D ../LICENSE.txt $startdir/pkg/usr/share/licenses/python-rst2pdf/COPYING
install -D doc/rst2pdf.1 $startdir/pkg/usr/share/man/man1/rst2pdf.1

And that's all you need to know about the process of packaging your app for Linux. It's easy to do, and most of the time, easy to do right!

Now, let's go to our final section...

Windows for the developer

First, remember that of relying on the system's version of Qt? Forget it, there is no system version available. And no python either. And noone is going to install it or your app, so it's "ship everything yourself" mode, or nothing.

But anyway, PyInstaller works for Windows too! So, using the same spec file, it works. Right?

Well, no beause of two problems.

Problem 1: You need an installer

Users are not going to open a zip somewhere, then do a shortcut to the binary on Windows, so you need to do some operations, and that means an installer.

Here's what I came up with to use NSIS, a free installer creator for Windows:

;Include Modern UI

!include "MUI2.nsh"


;Name and file
Name "Marave"
OutFile "Marave-0.5.win32.exe"

;Default installation folder
InstallDir "$LOCALAPPDATA\Marave"

;Get installation folder from registry if available
InstallDirRegKey HKCU "Software\Marave" ""

;Request application privileges for Windows Vista
RequestExecutionLevel user

;Interface Settings






!insertmacro MUI_LANGUAGE "English"

;Installer Sections

Section "Install"

SetOutPath "$INSTDIR"
File /r "dist\marave"

;Store installation folder
WriteRegStr HKCU "Software\Marave" "" $INSTDIR

;Create uninstaller
WriteUninstaller "$INSTDIR\Uninstall.exe"

;Create shortcuts
CreateDirectory $SMPROGRAMS\Marave
CreateShortCut "$SMPROGRAMS\Marave\Marave.lnk" "$INSTDIR\marave\marave.exe" ; use defaults for parameters, icon, etc.
CreateShortCut "$SMPROGRAMS\Marave\Uninstall Marave.lnk" "$INSTDIR\Uninstall.exe" ; use defaults for parameters, icon, etc.


;Uninstaller Section

Section "Uninstall"

Delete "$INSTDIR\Uninstall.exe"

DeleteRegKey /ifempty HKCU "Software\Marave"


It's comparable to the effort of building a packaging file, really, except every time you want to test it... you install it. There is no way (AFAICS) to see what's inside the installer except running it!

When things fail, you get no error messages, at least not the kind that is useful for a developer, the guy that needs to know what went wrong.

And after it's finished, you may end with a non-working program because of...

Problem 2: system libraries don't exist

Python 2.6 binaries are built using Visual Studio. That means they require the Visual Studio Runtime, specifically MSVCR90.DLL. That contains what on Linux would be considered part of libc. (linux guy: imagine apps that depend on a specific libc... hard to do!)

On Linux that's part of the system. Further, if you wanted, you can redistribute it. On Windows... well, it's a bit different.

  1. It's part of the "Visual C++ redistributables"

  2. Installing that doesn't guarantee it will work (yes, I have tried)

  3. The license for those 'redistributables' says you can't make them available for download.

    I have been told that including that in your installer is fine and dandy, but how is that not making them available for download?

So what can you do when you need a library and can't ship it and the user won't install it?

Well, that's why there is no Windows binary of Marave yet. Of course if anyone can help, I'd be really, really happy!

2010-02-09 16:04

Marave 0.4 is out!

Version 0.4 of Marave, a distraction-free fullscreen editor is out at

This version includes several bugs fixed and features implemented since 0.4:

  • It works better with WindowMaker (dialogs appeared behind main window)
  • Works better with some Qt styles (combo boxes were unusable)
  • Added support for SVG backgrounds
  • Code cleanups

Marave is free softare released under the GPL, and should work in all major desktop platforms.

I would love feedback on this release, as well as ideas for Marave's future, so if you want to help, please join the mailing list:

Of course, if you like Marave, feel free to give me money

Contents © 2000-2018 Roberto Alsina