I've been working on learning Python and PyQt for a few months now. I slowly come across various problems, and end up spending varying amounts of time finding solutions to the problems. One issue I find is that there's a lot of incomplete or incorrect examples floating around out there, which makes parsing through the possibilities somewhat difficult.

After reading a post about PyQt crashing, fatalsaint posted some code using a python lambda function to use with a clicked() signal to send to a slot/function. This is pretty helpful, and I thought there might be more useful tips out there people have, so I started this thread. This can include code snippets or sites out there that are helpful. This really isn't meant to be a question thread, though, just something to look through for ideas.

Here's a quick go of a few that I can quickly think of:

Identify the sender of a signal in a slot
This is a helpful snippet that effectively allows you to pass an argument to a clicked() signal. This is helpful when you don't want to have a lot of functions around, and you can simply use code inside a single function to do something.

How to use Qt Designer .ui files
I like to use Qt Designer to design forms and then output the .ui files, from there, you can use pyuic4 to turn them into .py files. I had a hard time grasping how to use the .py files from there. I found this link helpful in a way I could understand. Some people prefer to integrate the object creation directly into their code, which is fine, but I have a lot of issues with doing that.


Qt Documentation
While the official PyQt documentation is nice, I've found some really nice things with the official Qt Documentation. One is that you can easily find all members available for an object. There's also some nice documentation about various frameworks within Qt.

Learn to use Qt CSS
Much like web development, CSS is also available within Qt. There's a list of examples that can be tried out just using Qt Designer. If you're using custom CSS, using palette() in your CSS definitions will allow you to use colors that the theme already knows about. As an example, this is an easy way to get the default blue color on your buttons when you want that color.

Depending on your needs, there's a number of built-in icons that are available for use.

Getting native Maemo feeling windows
I know this is covered elsewhere here, but I thought I'd throw it in here, too. To get nice slidey maemo-like windows in pyqt, do something like the following

This will allow you to have the stacked effect with the windows making it look & feel like a 'real' Maemo application.

Are there other tips for common problems you've come across when working with PyQt that might be helpful for other people?

You're better looking at the Maemo version of the Qt documentation instead of the generic version. It includes documentation for the QtMaemo5 module, as well as some Maemo-specific platform notes.

might be worth listing all of the apps that are PyQt in the repos. That way you can just look at the actual real live examples here is my starter for 10.

ncalc
nclock
maesynth
maelophone
healthcheck

Lots of python gtk apps which dont get counted

Thanks for this, I suppose it make sense. This one from notes, specifically, I've had some issues with:

Style sheets and the native QMaemo5Style do not mix very well, since Maemo 5 lays out and draws some widgets very differently (e.g. QRadioButton). We recommend using local style sheets on specific widgets only, instead of setting one via QApplication::setStyleSheet().


But i don't *like* the maemo5style on some widgets!

This is a good idea - i'd find it immensely more useful having links to the actual source, though. I don't have time atm to go through the list and add links to source.

khteditor appears to be a port of pygtkedtor to Qt (I haven't actually tried it), but the source has some good things in it.

maesynth has a cool method of using images to draw the keys on the keyboard and using them to play sounds instead of normal Qt Widgets.

in healthchecks case, install it and you have the source

maesynth uses QGraphicsview

For identifying senders of a signal, I would recommend the blog post that just came up on planet.python.org

http://pysnippet.blogspot.com/2010/0...r-service.html

I'm wanting to write my new apps in PyQt. As such I have a roadmap of programs that stress various corner cases that I plan to port. I plan to start a blog and make a series about the lessons learned.

• Gonvert (Learning basic PyQt): Already Ported
• ejpi (Learning custom widgets for my pie menus)
• Dialcentral (Threading)
• An unnamed unreleased piece of software (all of the above plus GStreamer)

Eventually we should organize all of these into a wiki page (like what I did for Python and performance).

Yeah, a wiki page would be good.

Thanks for the input, everyone.

Avoid QThread

Threads cause a lot of problems and are difficult to use in many ways. Qt has a 'QTimer' mechanism that allows processing time to be shared so that events don't block the GUI.

This example seems to be pretty good and outline the different kinds of QTimers.

QTimers don't seem to work well with python-level blocking items, like putting a time.sleep(5) will pause everything. I'm not sure if there's a way to make this work or not.

PyQt Examples
There's the examples that come with the PyQt downloads that are written in Python and can be of use to figure out how to do something. It took me awhile to realize that the examples were also available in Python, which is handy to look at the source to figure out how to do something.

About threading. I haven't fully explore this yet since I haven't gotten to my relevant projects yet. I did read some material that suggest polling in an idle handler to push things back to the UI thread.

I was planning on experimenting with gobject . In theory Qt switched to the gobject main loop which means I should be able to use gobject callbacks. I use the idle and timeout callbacks to push tasks between threads in my PyGTK apps and is all the synchronization I need.

(It saddens me that Qt doesn't have thread safe signals/slots like gobject/GTK do)