PyQt or PySide - which one to use [closed]

Both toolkits are actively maintained, and by now more or less equal in features and quality. There are only few, rather unimportant differences.

Still, I'd recommend PySide for Python 2. It has a more reasonable API, mainly it doesn't expose Qt types, which have a direct equivalent in Python (e.g. QString, QList, etc.) or which are completely superfluous due to Python's dynamic nature, like QVariant. This avoids many tedious conversions to and from Qt types, and thus eases programming and avoids many errors.

PyQt also supports this modern API, and uses it by default for Python 3, but not for Python 2 to maintain backwards compatibility.

There is also the licensing difference. PySide is LGPL while PyQt is GPL. This could make a difference if you don't wish to make your project opensource. Although PyQt always has the propriety version available for a fairly reasonable price.

I tend to find the PySide documentation more intuitive. The API, in my opinion is slightly more Pythonic and the rate of bug fixes is quite impressive at the moment.

PyQt has the advantage of Python 3 support and incumbency. There is a lot more 3rd party documentation/tutorials for it.

I recently ported a significant code base (over 8,000 lines of code) from PyQt to PySide.

Right now I'd say PyQt is a much more mature, performant and stable project. I hit a number of bugs in PySide, and suspect that any big project will hit issues. Having said that, I reported a bug to the project and it was fixed and in a new release within a few weeks. I'm also having a problem where the app takes about 15 seconds to quit. I've not yet spent the time to find out why. However it's only a matter of time before there will be no reasons for choosing PyQt over PySide.

If you do decide to go with PyQt for now, make sure you use API v2 throughout. It is a better API, and will ease any future transition to PySide. Also if you do port, just follow the guidelines on the PySide wiki. Even for an 8+ kloc app consisting of about 20 source files it just took an afternoon.