Posts about pyqt (old posts, page 6)

2011-07-24 21:20

Shipping your PyQt app for windows

I have written about this in the past, with the general conclusion being "it's a pain in the ass".

So, now, here is how it's done.

  1. Start with a working PyQt application. In this example, I will use devicenzo.py mostly because:
    1. It is a working PyQt application.
    2. It uses a big chunk of PyQt
    3. It's easy to test
  2. Now you need a setup.py. Here's one that works, with extensive commments.
# We will be using py2exe to build the binaries.
# You may use other tools, but I know this one.

from distutils.core import setup
import py2exe

# Now you need to pass arguments to setup
# windows is a list of scripts that have their own UI and
# thus don't need to run in a console.

setup(windows=['devicenzo.py'],
      options={

# And now, configure py2exe by passing more options;

          'py2exe': {

# This is magic: if you don't add these, your .exe may
# or may not work on older/newer versions of windows.

              "dll_excludes": [
                  "MSVCP90.dll",
                  "MSWSOCK.dll",
                  "mswsock.dll",
                  "powrprof.dll",
                  ],

# Py2exe will not figure out that you need these on its own.
# You may need one, the other, or both.

              'includes': [
                  'sip',
                  'PyQt4.QtNetwork',
                  ],

# Optional: make one big exe with everything in it, or
# a folder with many things in it. Your choice
#             'bundle_files': 1,
          }
      },

# Qt's dynamically loaded plugins and py2exe really don't
# get along.

data_files = [
            ('phonon_backend', [
                'C:\Python27\Lib\site-packages\PyQt4\plugins\phonon_backend\phonon_ds94.dll'
                ]),
            ('imageplugins', [
            'c:\Python27\lib\site-packages\PyQt4\plugins\imageformats\qgif4.dll',
            'c:\Python27\lib\site-packages\PyQt4\plugins\imageformats\qjpeg4.dll',
            'c:\Python27\lib\site-packages\PyQt4\plugins\imageformats\qsvg4.dll',
            ]),
],

# If you choose the bundle above, you may want to use this, too.
#     zipfile=None,
)
  1. Run python setup.py py2exe and get a dist folder full of binary goodness.

And that's it. Except of course, that's not it.

What this will do is create a binary set, either a folder full of things, or a single EXE file. And that's not enough. You have to consider at least the following:

  1. Put everything in resource files: images, qss files, icons, etc. Every file your app needs? Put it in a resource file and load it from there. That way you don't have to care about them if you go the "one exe" road.
  2. Compile .ui files to .py (same reason)
  3. Figure out if you use Qt's plugins, and make them work. This includes: using Phonon, using QtSQL, and using any image formats other than PNG.

After you have that, are you done? NO!

Your windows user will want an installer. I am not going to go into details, but I had a good time using BitRock's InstallBuilder for Qt. It's a nice tool, and it works. That's a lot in this field.

But is that all? NO!

You have to take care of the Visual Studio Runtime. My suggestion? Get a copy of the 1.1MB vcredist_x86.exe (not the larger one, the 1.1MB one), and either tell people to install it manually, or add it to your installer. You are legally allowed (AFAIK) to redistribute that thing as a whole. But not what's in it (unless you have a VS license).

And we are done? NO!

Once you run your app "installed", if it ever prints anything to stderr, you will get either a dialog telling you it did, or worse (if you are in aything newer than XP), a dialog telling you it can't write to a log file, and the app will never work again.

This is because py2exe catches stderr and tries to save it on a logfile. Which it tries to create in the same folder as the binary. Which is usually not allowed because of permissions.

Solution? Your app should never write to stderr. Write an excepthook and catch that. And then remove stderr or replace it with a log file, or something. Just don't let py2exe do it, because the way py2exe does it is broken.

And is that it?

Well, basically yes. Of course you should get 4 or 5 different versions of windows to test it on, but you are pretty much free to ship your app as you wish. Oh, mind you, don't upload it to downloads.com because they will wrap your installer in a larger one that installs bloatware and crap.

So, there you go.

2011-03-11 01:47

New golfing challenge: PatoCabrera

In the spirit of the De Vicenzo web browser, I am starting a new program, called Pato Cabrera. Here are the rules:

  • Twitter client (no identi.ca in the first version, but to be added later)
  • Has these features: http://pastebin.lugmen.org.ar/6464
  • Has to be implemented before April 4th
  • Smaller than 16384 bytes (of python code) but may be larger because of artwork.

Let's see how it works :-)

2011-03-08 21:45

OK, so THAT is how much browser I can put in 128 lines of code.

I have already posted a couple of times (1, 2) about De Vicenzo , an attempt to implement the rest of the browser, starting with PyQt's WebKit... limiting myself to 128 lines of code.

Of course I could do more, but I have my standards!

  • No using ;
  • No if whatever: f()

Other than that, I did a lot of dirty tricks, but right now, it's a fairly complete browser, and it has 127 lines of code (according to sloccount) so that's enough playing and it's time to go back to real work.

But first, let's consider how some features were implemented (I'll wrap the lines so they page stays reasonably narrow), and also look at the "normal" versions of the same (the "normal" code is not tested, please tell me if it's broken ;-).

This is not something you should learn how to do. In fact, this is almost a treatise on how not to do things. This is some of the least pythonic, less clear code you will see this week.

It is short, and it is expressive. But it is ugly.

I'll discuss this version.

Proxy Support

A browser is not much of a browser if you can't use it without a proxy, but luckily Qt's network stack has good proxy support. The trick was configuring it.

De Vicenzo supports HTTP and SOCKS proxies by parsing a http_proxy environment variable and setting Qt's application-wide proxy:

 proxy_url = QtCore.QUrl(os.environ.get('http_proxy', ''))
 QtNetwork.QNetworkProxy.setApplicationProxy(QtNetwork.QNetworkProxy(\
 QtNetwork.QNetworkProxy.HttpProxy if unicode(proxy_url.scheme()).startswith('http')\
 else QtNetwork.QNetworkProxy.Socks5Proxy, proxy_url.host(),\
 proxy_url.port(), proxy_url.userName(), proxy_url.password())) if\
'http_proxy' in os.environ else None

How would that look in normal code?

if 'http_proxy' in os.environ:
    proxy_url = QtCore.QUrl(os.environ['http_proxy'])
    if unicode(proxy_url.scheme()).starstswith('http'):
        protocol = QtNetwork.QNetworkProxy.HttpProxy
    else:
        protocol = QtNetwork.QNetworkProxy.Socks5Proxy
    QtNetwork.QNetworkProxy.setApplicationProxy(
        QtNetwork.QNetworkProxy(
            protocol,
            proxy_url.host(),
            proxy_url.port(),
            proxy_url.userName(),
            proxy_url.password()))

As you can see, the main abuses against python here are the use of the ternary operator as a one-line if (and nesting it), and line length.

Persistent Cookies

You really need this, since you want to stay logged into your sites between sessions. For this, first I needed to write some persistence mechanism, and then save/restore the cookies there.

Here's how the persistence is done (settings is a global QSettings instance):

def put(self, key, value):
    "Persist an object somewhere under a given key"
    settings.setValue(key, json.dumps(value))
    settings.sync()

def get(self, key, default=None):
    "Get the object stored under 'key' in persistent storage, or the default value"
    v = settings.value(key)
    return json.loads(unicode(v.toString())) if v.isValid() else default

It's not terribly weird code, except for the use of the ternary operator in the last line. The use of json ensures that as long as reasonable things are persisted, you will get them with the same type as you put them without needing to convert them or call special methods.

So, how do you save/restore the cookies? First, you need to access the cookie jar. I couldn't find whether there is a global one, or a per-webview one, so I created a QNetworkCookieJar in line 24 and assign it to each web page in line 107.

# Save the cookies, in the window's closeEvent
self.put("cookiejar", [str(c.toRawForm()) for c in self.cookies.allCookies()])

# Restore the cookies, in the window's __init__
self.cookies.setAllCookies([QtNetwork.QNetworkCookie.parseCookies(c)[0]\
for c in self.get("cookiejar", [])])

Here I confess I am guilty of using list comprehensions when a for loop would have been the correct thing.

I use the same trick when restoring the open tabs, with the added misfeature of using a list comprehension and throwing away the result:

# get("tabs") is a list of URLs
[self.addTab(QtCore.QUrl(u)) for u in self.get("tabs", [])]

Using Properties and Signals in Object Creation

This is a feature of recent PyQt versions: if you pass property names as keyword arguments when you create an object, they are assigned the value. If you pass a signal as a keyword argument, they are connected to the given value.

This is a really great feature that helps you create clear, local code, and it's a great thing to have. But if you are writing evil code... well, you can go to hell on a handbasket using it.

This is all over the place in De Vicenzo, and here's one example (yes, this is one line):

QtWebKit.QWebView.__init__(self, loadProgress=lambda v:\
(self.pbar.show(), self.pbar.setValue(v)) if self.amCurrent() else\
None, loadFinished=self.pbar.hide, loadStarted=lambda:\
self.pbar.show() if self.amCurrent() else None, titleChanged=lambda\
t: container.tabs.setTabText(container.tabs.indexOf(self), t) or\
(container.setWindowTitle(t) if self.amCurrent() else None))

Oh, boy, where do I start with this one.

There are lambda expressions used to define the callbacks in-place instead of just connecting to a real function or method.

There are lambdas that contain the ternary operator:

loadStarted=lambda:\
    self.pbar.show() if self.amCurrent() else None

There are lambdas that use or or a tuple to trick python into doing two things in a single lambda!

loadProgress=lambda v:\
(self.pbar.show(), self.pbar.setValue(v)) if self.amCurrent() else\
None

I won't even try to untangle this for educational purposes, but let's just say that line contains what should be replaced by 3 methods, and should be spread over 6 lines or more.

Download Manager

Ok, calling it a manager is overreaching, since you can't stop them once they start, but hey, it lets you download things and keep on browsing, and reports the progress!

First, on line 16 I created a bars dictionary for general bookkeeping of the downloads.

Then, I needed to delegate the unsupported content to the right method, and that's done in lines 108 and 109

What that does is basically that whenever you click on something WebKit can't handle, the method fetch will be called and passed the network request.

def fetch(self, reply):
    destination = QtGui.QFileDialog.getSaveFileName(self, \
        "Save File", os.path.expanduser(os.path.join('~',\
            unicode(reply.url().path()).split('/')[-1])))
    if destination:
        bar = QtGui.QProgressBar(format='%p% - ' +
            os.path.basename(unicode(destination)))
        self.statusBar().addPermanentWidget(bar)
        reply.downloadProgress.connect(self.progress)
        reply.finished.connect(self.finished)
        self.bars[unicode(reply.url().toString())] = [bar, reply,\
            unicode(destination)]

No real code golfing here, except for long lines, but once you break them reasonably, this is pretty much the obvious way to do it:

  • Ask for a filename
  • Create a progressbar, put it in the statusbar, and connect it to the download's progress signals.

Then, of course, we need ths progress slot, that updates the progressbar:

progress = lambda self, received, total:\
    self.bars[unicode(self.sender().url().toString())][0]\
    .setValue(100. * received / total)

Yes, I defined a method as a lambda to save 1 line. [facepalm]

And the finished slot for when the download is done:

def finished(self):
    reply = self.sender()
    url = unicode(reply.url().toString())
    bar, _, fname = self.bars[url]
    redirURL = unicode(reply.attribute(QtNetwork.QNetworkRequest.\
        RedirectionTargetAttribute).toString())
    del self.bars[url]
    bar.deleteLater()
    if redirURL and redirURL != url:
        return self.fetch(redirURL, fname)
    with open(fname, 'wb') as f:
        f.write(str(reply.readAll()))

Notice that it even handles redirections sanely! Beyond that, it just hides the progress bar, saves the data, end of story. The longest line is not even my fault!

There is a big inefficiency in that the whole file is kept in memory until the end. If you download a DVD image, that's gonna sting.

Also, using with saves a line and doesn't leak a file handle, compared to the alternatives.

Printing

Again Qt saved me, because doing this manually would have been a pain. However, it turns out that printing is just ... there? Qt, specially when used via PyQt is such an awesomely rich environment.

self.previewer = QtGui.QPrintPreviewDialog(\
    paintRequested=self.print_)
self.do_print = QtGui.QShortcut("Ctrl+p",\
    self, activated=self.previewer.exec_)

There's not even any need to golf here, that's exactly as much code as you need to hook Ctrl+p to make a QWebView print.

Other Tricks

There are no other tricks. All that's left is creating widgets, connecting things to one another, and enjoying the awesome experience of programming PyQt, where you can write a whole web browser (except the engine) in 127 lines of code.

2011-03-05 23:46

De Vicenzo: A much cooler mini web browser.

It seems it was only a few days ago that I started this project. Oh, wait, yes, it was just a few days ago!

If you don't want to read that again, the idea is to see just how much code is needed to turn Qt's WebKit engine into a fully-fledged browser.

To do that, I set myself a completely arbitrary limit: 128 lines of code.

So, as of now, I declare it feature-complete.

The new features are:

  • Tabbed browsing (you can add/remove tabs)
  • Bookmarks (you can add/remove them, and choose them from a drop-down menu)

This is what already worked:

  • Zoom in (Ctrl++)
  • Zoom out (Ctrl+-)
  • Reset Zoom (Ctrl+=)
  • Find (Ctrl+F)
  • Hide find (Esc)
  • Buttons for back/forward and reload
  • URL entry that matches the page + autocomplete from history + smart entry (adds http://, that kind of thing)
  • Plugins support (including flash)
  • The window title shows the page title (without browser advertising ;-)
  • Progress bar for page loading
  • Statusbar that shows hovered links URL
  • Takes a URL on the command line, or opens http://python.org
  • Multiplatform (works in any place QtWebKit works)

So... how much code was needed for this? 87 LINES OF CODE

Or if you want the PEP8-compliant version, 115 LINES OF CODE.

Before anyone says it: yes, I know the rendering engine and the toolkit are huge. What I wrote is just the chrome around them, just like Arora, Rekonq, Galeon, Epiphany and a bunch of others do.

It's simple, minimalistic chrome, but it works pretty good, IMVHO.

Here it is in (buggy) action:

It's more or less feature-complete for what I expected to be achievable, but it still needs some fixes.

You can see the code at it's own home page: http://devicenzo.googlecode.com

2011-02-28 21:10

How much web browser can you put in 128 lines of code?

UPDATE: If you read this and all you can say is "oh, he's just embedding WebKit", I have two things to tell you:

  1. Duh! Of course the 128 lines don't include the rendering engine, or the TCP implementation, or the GUI toolkit. This is about the rest of the browser, the part around the web rendering engine. You know, just like Arora, Rekonq, Epiphany, and everyone else that embeds webkit or mozilla does it? If you didn't get that before this explanation... facepalm.
  2. Get your favourite webkit fork and try to do this much with the same amount of code. I dare you! I double dog dare you!

Now back to the original article


Today, because of a IRC chat, I tried to find a 42-line web browser I had written a while ago. Sadly, the pastebin where I posted it was dead, so I learned a lesson: It's not a good idea to trust a pastebin as code repository

What I liked about that 42-line browser was that it was not the typical example, where someone dumps a Webkit view in a window, loads a page and tries to convince you he's cool. That one is only 7 lines of code:

import sys
from PyQt4 import QtGui,QtCore,QtWebKit
app=QtGui.QApplication(sys.argv)
wb=QtWebKit.QWebView()
wb.setUrl(QtCore.QUrl('http://www.python.org'))
wb.show()
sys.exit(app.exec_())

And if I wanted to make the code uglier, it could be done in 6.

But anyway, that 42-line browser actually looked useful!

This 42-line web browser, courtesy of #python and #qt -- http... on Twitpic

Those buttons you see actually worked correctly, enabling and disabling at the right moment, the URL entry changed when you clicked on links, and some other bits.

So, I have decided to start a small, intermittent project of code golf: put as much browser as I can in 128 lines of code (not counting comments or blanks), starting with PyQt4.

This has a useful purpose: I always suspected that if you assumed PyQt was part of the base system, most apps would fit in floppies again. This one fits on a 1.44MB floppy some 500 times (so you could use 360KB commodore floppies if you prefer!).

So far, I am at about 50 lines, and it has the following features:

  • Zoom in (Ctrl++)
  • Zoom out (Ctrl+-)
  • Reset Zoom (Ctrl+=)
  • Find (Ctrl+F)
  • Hide find (Esc)
  • Buttons for back/forward and reload
  • URL entry that matches the page + autocomplete from history + smart entry (adds http://, that kind of thing)
  • Plugins support (including flash)
  • The window title shows the page title (without browser advertising ;-)
  • Progress bar for page loading
  • Statusbar that shows hovered links URL
  • Takes a URL on the command line, or opens http://python.org
  • Multiplatform (works in any place QtWebKit works)

Missing are tabs and proxy support. I expect those will take another 40 lines or so, but I think it's probably the most featureful of these toy browsers.

The code... it's not all that hard. I am using lambda a lot, and I am using PyQt's keyword arguments for signal connection which makes lines long, but not hard. It could be made much smaller!

Here it is in action:

And here's the code:

#!/usr/bin/env python
"A web browser that will never exceed 128 lines of code. (not counting blanks)"

import sys
from PyQt4 import QtGui,QtCore,QtWebKit

class MainWindow(QtGui.QMainWindow):
    def __init__(self, url):
        QtGui.QMainWindow.__init__(self)
        self.sb=self.statusBar()

        self.pbar = QtGui.QProgressBar()
        self.pbar.setMaximumWidth(120)
        self.wb=QtWebKit.QWebView(loadProgress = self.pbar.setValue, loadFinished = self.pbar.hide, loadStarted = self.pbar.show, titleChanged = self.setWindowTitle)
        self.setCentralWidget(self.wb)

        self.tb=self.addToolBar("Main Toolbar")
        for a in (QtWebKit.QWebPage.Back, QtWebKit.QWebPage.Forward, QtWebKit.QWebPage.Reload):
            self.tb.addAction(self.wb.pageAction(a))

        self.url = QtGui.QLineEdit(returnPressed = lambda:self.wb.setUrl(QtCore.QUrl.fromUserInput(self.url.text())))
        self.tb.addWidget(self.url)

        self.wb.urlChanged.connect(lambda u: self.url.setText(u.toString()))
        self.wb.urlChanged.connect(lambda: self.url.setCompleter(QtGui.QCompleter(QtCore.QStringList([QtCore.QString(i.url().toString()) for i in self.wb.history().items()]), caseSensitivity = QtCore.Qt.CaseInsensitive)))

        self.wb.statusBarMessage.connect(self.sb.showMessage)
        self.wb.page().linkHovered.connect(lambda l: self.sb.showMessage(l, 3000))

        self.search = QtGui.QLineEdit(returnPressed = lambda: self.wb.findText(self.search.text()))
        self.search.hide()
        self.showSearch = QtGui.QShortcut("Ctrl+F", self, activated = lambda: (self.search.show() , self.search.setFocus()))
        self.hideSearch = QtGui.QShortcut("Esc", self, activated = lambda: (self.search.hide(), self.wb.setFocus()))

        self.quit = QtGui.QShortcut("Ctrl+Q", self, activated = self.close)
        self.zoomIn = QtGui.QShortcut("Ctrl++", self, activated = lambda: self.wb.setZoomFactor(self.wb.zoomFactor()+.2))
        self.zoomOut = QtGui.QShortcut("Ctrl+-", self, activated = lambda: self.wb.setZoomFactor(self.wb.zoomFactor()-.2))
        self.zoomOne = QtGui.QShortcut("Ctrl+=", self, activated = lambda: self.wb.setZoomFactor(1))
        self.wb.settings().setAttribute(QtWebKit.QWebSettings.PluginsEnabled, True)

        self.sb.addPermanentWidget(self.search)
        self.sb.addPermanentWidget(self.pbar)
        self.wb.load(url)


if __name__ == "__main__":
    app=QtGui.QApplication(sys.argv)
    if len(sys.argv) > 1:
        url = QtCore.QUrl.fromUserInput(sys.argv[1])
    else:
        url = QtCore.QUrl('http://www.python.org')
    wb=MainWindow(url)
    wb.show()
    sys.exit(app.exec_())

2010-12-02 12:20

Charla: aplicaciones extensibles con PyQt

Spanish only, since it's about a video in spanish ;-)

Acá está, gracias a la gente de Junín, un video de mi charla "Aplicaciones extensibles usando PyQt", en la que intento mostrar como desarrollar una aplicación con PyQt y yapsy.

No es una charla con la que esté muy contento. La otra salió mejor, pero no se filmó, así que quedará solo en la memoria de los cuatro gatos locos que estábamos ahí ;-)

El resto de las charlas: http://unnoba.blip.tv/

2010-10-01 15:12

Making your app modular: Yapsy

That a plugin architecture for a complex app is a good idea is one of those things that most people kinda agree on. One thing we don't quite agree is how the heck are we going to make out app modular?

One way to do it (if you are coding python) is using Yapsy.

Yapsy is awesome. Also, yapsy is a bit underdocumented. Let's see if this post fixes that a bit and leaves just the awesome.

Update: I had not seen the new Yapsy docs, released a few days ago. They are much better than what was there before :-)

Here's the general idea behind yapsy:

  • You create a Plugin Manager that can find and load plugins from a list of places (for example, from ["/usr/share/appname/plugins", "~/.appname/plugins"]).

  • A plugin category is a class.

  • There is a mapping between category names and category classes.

  • A plugin is a module and a metadata file. The module defines a class that inherits from a category class, and belongs to that category.

    The metadata file has stuff like the plugin's name, description, URL, version, etc.

One of the great things about Yapsy is that it doesn't specify too much. A plugin will be just a python object, you can put whatever you want there, or you can narrow it down by specifying the category class.

In fact, the way I have been doing the category classes is:

  • Start with an empty class
  • Implement two plugins of that category
  • If there is a chunk that's much alike in both, move it into the category class.

But trust me, this will all be clearer with an example :-)

I will be doing it with a graphical PyQt app, but Yapsy works just as well for headless of CLI apps.

Let's start with a simple app: an HTML editor with a preview widget.

//ralsina.me/static/yapsy/editor1.jpeg

A simple editor with preview

Here's the code for the app, which is really simple (it doesn't save or do anything, really, it's just an example):

editor1.py

from PyQt4 import QtCore, QtGui, QtWebKit
import os, sys

class Main(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.layout = QtGui.QVBoxLayout()
        self.editor = QtGui.QPlainTextEdit()
        self.preview = QtWebKit.QWebView()
        self.layout.addWidget(self.editor)
        self.layout.addWidget(self.preview)
        self.editor.textChanged.connect(self.updatePreview)
        self.setLayout(self.layout)

    def updatePreview(self):
        self.preview.setHtml(self.editor.toPlainText())

def main():
    # Again, this is boilerplate, it's going to be the same on
    # almost every app you write
    app = QtGui.QApplication(sys.argv)
    window=Main()
    window.show()
    # It's exec_ because exec is a reserved word in Python
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Note

From now on listings will not include the main function, because it never changes.

But this application has an obvious limit: you have to type HTML in it. Why not type python code in it and have it convert to HTML for display? Or Wiki markup, or restructured text?

You could, in principle, just implement all those modes, but then you are assuming the responsability of supporting every thing-that-can-be-turned-into-HTML. Your app would be a monolith. That's where yapsy enters the scene.

So, let's create a plugin category, called "Formatter" which takes plain text and returns HTML. Then we add stuff in the UI so the user can choose what formatter he wants, and implement two of those.

Here's our plugin category class:

categories.py

class Formatter(object):
    """Plugins of this class convert plain text to HTML"""

    name = "No Format"

    def formatText(self, text):
        """Takes plain text, returns HTML"""
        return text

Of course what good is a plugin architecture without any plugins for it? So, let's create two plugins.

First: a plugin that takes python code and returns HTML, thanks to pygments.

plugins/pygmentize.py

from pygments import highlight
from pygments.lexers import PythonLexer
from pygments.formatters import HtmlFormatter

from categories import Formatter

class Pygmentizer(Formatter):
    name = "Python Code"

    def formatText(self, text):
        return highlight(text, PythonLexer(), HtmlFormatter(full=True))

See how it goes into a plugins folder? Later on we will tell yapsy to search there for plugins.

To be recognized as a plugin, it needs a metadata file, too:

plugins/pygmentize.yapsy-plugin

[Core]
Name = Python Code
Module = pygmentize

[Documentation]
Author = Roberto Alsina
Version = 0.1
Website = //ralsina.me
Description = Highlights Python Code

And really, that's all there is to making a plugin. Here's another one for comparison, which uses docutils to format reStructured Text:

plugins/rest.py

from categories import Formatter
import docutils.core
import docutils.io


class Rest(Formatter):
    name = "Restructured Text"

    def formatText(self, text):
        output = docutils.core.publish_string(
            text, writer_name = 'html'
        )
        return output

plugins/rest.yapsy-plugin

[Core]
Name = Restructured Text
Module = rest

[Documentation]
Author = Roberto Alsina
Version = 0.1
Website = //ralsina.me
Description = Formats restructured text

And here they are in action:

//ralsina.me/static/yapsy/editor2.jpeg

reSt mode

//ralsina.me/static/yapsy/editor3.jpeg

Python mode

Of course using categories you can do things like a "Tools" category, where the plugins get added to a Tools menu, too.

And here's the application code:

editor2.py

from categories import Formatter
from yapsy.PluginManager import PluginManager

class Main(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.layout = QtGui.QVBoxLayout()
        self.formattersCombo = QtGui.QComboBox()
        self.editor = QtGui.QPlainTextEdit()
        self.preview = QtWebKit.QWebView()

        self.layout.addWidget(self.formattersCombo)
        self.layout.addWidget(self.editor)
        self.layout.addWidget(self.preview)

        self.editor.textChanged.connect(self.updatePreview)
        self.setLayout(self.layout)

        # Create plugin manager
        self.manager = PluginManager(categories_filter={ "Formatters": Formatter})
        self.manager.setPluginPlaces(["plugins"])

        # Load plugins
        self.manager.locatePlugins()
        self.manager.loadPlugins()

        # A do-nothing formatter by default
        self.formattersCombo.addItem("None")
        self.formatters = {}
        print self.manager.getPluginsOfCategory("Formatters")
        for plugin in self.manager.getPluginsOfCategory("Formatters"):
            print  "XXX"
            # plugin.plugin_object is an instance of the plugin
            self.formattersCombo.addItem(plugin.plugin_object.name)
            self.formatters[plugin.plugin_object.name] = plugin.plugin_object

    def updatePreview(self):
        # Check what the current formatter is
        name =  unicode(self.formattersCombo.currentText())
        text = unicode(self.editor.toPlainText())
        if name in self.formatters:
            text = self.formatters[name].formatText(text)
        self.preview.setHtml(text)

In short: this is easy to do, and it leads to fixing your application's internal structure, so it helps you write better code.

Full source code for everything.

2010-09-23 22:33

eBooks and PyQt: a good match

I have been putting lots of love into Aranduka an eBook manager, (which is looking very good lately, thanks!), and I didn't want it to also be an eBook reader.

But then I thought... how hard can it be to read ePub? Well, it's freaking easy!

Here's a good start at stackoverflow.com but the short of it is... it's a zip with some XML in it.

One of those XML files tells you where things are, one of them is the TOC, the rest is just a small static collection of HTML/CSS/images.

So, here are the ingredients to roll-your-own ePub reader widget in 150 LOC:

  • Use python's zipfile library to avoid exploding the zip (that's lame)
  • Use Element Tree to parse said XML files.
  • Use PyQt's QtWebKit to display said collection of XML/CSS/Images
  • Use this recipe to make QtWebKit tell you when it wants something from the zipfile.

Plug some things to others, shake vigorously, and you end up with this:

Share photos on twitter with Twitpic

Here's the code (as of today) and the UI file you need.

Missing stuff:

  • It doesn't display the cover.
  • It only shows the top level of the table of contents.
  • I only tested it on two books ;-)
  • It sure can use a lot of refactoring!

Neither should be terribly hard to do.

2010-09-18 01:55

Introducing Aranduka

Yes, it's yet another program I am working on. But hey, the last few I started are actually pretty functional already!

And... I am not doing this one alone, which should make it more fun.

It's an eBook (or just any book?) manager, that helps you keep your PDF/Mobi/FB2/whatever organized, and should eventually sync them to the device you want to use to read them.

What works now? See the video!

In case that makes no sense to you:

  • You can get books from FeedBooks. Those books will get downloaded, added to your database, tagged, the cover fetched, etc. etc.

  • You can import your current folder of books in bulk.

    Aranduka will use google and other sources to try to guess (from the filename) what book that is and fill in the extra data about it.

  • You can "guess" the extra data.

    By marking certain data (say, the title) as reliable, Aranduka will try to find some possible books that match then you can choose if it's right.

    Of course you can also edit that data manually.

And that's about it. Planned features:

  • Way too many to list.

The goals are clear:

  • It should be beautiful (I know it isn't!)
  • It should be powerful (not yet!)
  • It should be better than the "competition"

If those three goals are not achieved, it's failure. It may be a fun failure, but it would still be a failure.

2010-09-14 12:56

Very pythonic progress dialogs.

Sometimes, you see a piece of code and it just feels right. Here's an example I found when doing my "Import Antigravity" session for PyDay Buenos Aires: the progressbar module.

Here's an example that will teach you enough to use progressbar effectively:

progress = ProgressBar()
for i in progress(range(80)):
    time.sleep(0.01)

Yes, that's it, you will get a nice ASCII progress bar that goes across the terminal, supports resizing and moves as you iterate from 0 to 79.

The progressbar module even lets you do fancier things like ETA or fie transfer speeds, all just as nicely.

Isn't that code just right? You want a progress bar for that loop? Wrap it and you have one! And of course since I am a PyQt programmer, how could I make PyQt have something as right as that?

Here'show the output looks like:

progress

You can do this with every toolkit, and you probably should!. It has one extra feature: you can interrupt the iteration. Here's the (short) code:

# -*- coding: utf-8 -*-
import sys, time
from PyQt4 import QtCore, QtGui

def progress(data, *args):
    it=iter(data)
    widget = QtGui.QProgressDialog(*args+(0,it.__length_hint__()))
    c=0
    for v in it:
        QtCore.QCoreApplication.instance().processEvents()
        if widget.wasCanceled():
            raise StopIteration
        c+=1
        widget.setValue(c)
        yield(v)

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)

    # Do something slow
    for x in progress(xrange(50),"Show Progress", "Stop the madness!"):
        time.sleep(.2)

Have fun!

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