[PyQt] pyqtsignal() and None value

J Barchan jnbarchan at gmail.com
Tue Sep 4 17:16:59 BST 2018

PyQt5.7.  I am having trouble `emit()`ing a signal and receiving its
arguments correctly.  I have read
http://pyqt.sourceforge.net/Docs/PyQt5/signals_slots.html carefully.


    # class variable for "notifyProgress" signal, for displaying a
    notifyProgress = QtCore.pyqtSignal(int, str)




    def updateProgress(self, val: int, text: str):
        # slot for self.notifyProgress
        # eprpayrequestfunctions.runEpr() calls this to indicate progress
        # if it passes an integer it's the desired value for the progressbar
        # if it passes a string it's the desired value for the label
        if val is not None:
        if text is not None:


1. notifyProgress.emit(None, "Some text")

2. notifyProgress.emit(i / 2, None)

*Behaviour in slot*:

The problem is the passing of None from emit():

1. val arrives in slot as 1261196128.

2. text arrives in slot as '' (empty string).


   - Where is this behaviour for None as an emit() parameter documented?
   - What is the correct/best way for handling this correctly/easily?

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