Threading in PyQt Applications: Qt Threads vs. Python Threads

Developers seeking to create responsive GUI applications using PyQt often encounter the challenge of executing long-running tasks without hindering the UI's functionality. One solution is to utilize a separate thread for these tasks. This raises the question of whether to use Qt threads or the native Python threading module.

Qt threads offer comprehensive integration with the PyQt framework. Asychronous signals/slots, the event loop, and other functionalities are seamlessly handled within Qt threads. Moreover, interacting with Qt from a Python thread is not feasible, necessitating the use of a QThread for such interactions.

On the other hand, Python threads have the advantage of being able to utilize all CPU cores, as opposed to Qt threads, which are restricted to a single core. However, python threads require careful handling of GUI updates, as directly modifying GUI elements from a Python thread can lead to unpredictable behavior.

A general guideline provided by Giovanni Bajo, a PyQt developer, recommends using Qt threads when interacting with Qt, such as posting events to the main thread, and Python threads for tasks that do not require Qt interaction.

It is noteworthy that the underlying thread implementations for both Qt and Python threads are the same. Thus, the choice between the two primarily depends on the specific requirements of the application, with Qt threads being preferred for seamless integration with PyQt.