I am learning to program with PyQt5. No troubles with that, but there is one annoying issue: when I start the app, I immediately get the message that an exception occurred and SystemExit: -1 is repported (see below).
An exception has occurred, use %tb to see the full traceback.
SystemExit: -1
/home/arnold/bin/anaconda3/envs/ml-gpu/lib/python3.5/site-packages/IPython/core/interactiveshell.py:2918: UserWarning: To exit: use 'exit', 'quit', or Ctrl-D.
warn("To exit: use 'exit', 'quit', or Ctrl-D.", stacklevel=1)
In [2]: %tb
Traceback (most recent call last):
File "<ipython-input-1-f5ccc42a06e6>", line 1, in <module>
runfile('/media/d/home/arnold/development/python/course_Qt/01-basic-window.py', wdir='/media/d/home/arnold/development/python/course_Qt')
File "/home/arnold/bin/anaconda3/envs/ml-gpu/lib/python3.5/site-packages/spyder/utils/site/sitecustomize.py", line 692, in runfile
execfile(filename, namespace)
File "/home/arnold/bin/anaconda3/envs/ml-gpu/lib/python3.5/site-packages/spyder/utils/site/sitecustomize.py", line 101, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)
File "/media/d/home/arnold/development/python/course_Qt/01-basic-window.py", line 19, in <module>
sys.exit(app.exec_()) # mind the underscore, without is python function
SystemExit: -1
The program is a very simple one:
import sys
from PyQt5.QtWidgets import QApplication, QWidget
app = QApplication(sys.argv)
win = QWidget() # No arguments = toplevel window
win.setWindowTitle('Qt5 Window')
win.resize(640, 480)
win.show()
# wrap Qt5 call in sys.exit in order to catch any unhandled exception
# just good practice
sys.exit(app.exec_()) # mind the underscore, without is python function
The program runs fine after that, I can do all things what I want and normally exit. When I try to run the program again I get the message:
QCoreApplication::exec: The event loop is already running
I forcefully terminate the program and when I try to run it again it starts all over again. Is it my setup or is something else wrong? I could not find a hint when googling for this error.
Setup: linux min 18.3, Spyder 3.5, conda 4.4.11, PyQt 5.10.1
Update
The answer of Carlos below is the correct one. What I did not mention is that I used QtDesigner with PyQt5 and couldn't find a decent example for it. This is the best I could find and I adjusted it to the solution Carlos mentioned below. Save pyqt_first.py
and tax_calc.ui
, run pyuic5 -o tax_calc.py tax_calc.ui
and everything should run fine. Do not forget to set the graphics backend to inline
(Tools > Preferences > IPython console).
#--- pyqt_first.py ---
import sys
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QMainWindow
from tax_calc import Ui_MainWindow
class HelloWindow(QMainWindow, Ui_MainWindow):
def __init__(self):
QMainWindow.__init__(self)
Ui_MainWindow.__init__(self)
self.setupUi(self)
self.calc_tax_button.clicked.connect(self.CalculateTax)
def CalculateTax(self):
price = int(self.price_box.toPlainText())
tax = (self.tax_rate.value())
total_price = price + ((tax / 100) * price)
total_price_string = "The total price with tax is: " + str(total_price)
self.results_window.setText(total_price_string)
if __name__ == "__main__":
def run_app():
app = QtWidgets.QApplication(sys.argv)
mainWin = HelloWindow()
mainWin.show()
app.exec_()
run_app()
#--- tax_calc.ui ---
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>800</width>
<height>600</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralwidget">
<widget class="QTextEdit" name="price_box">
<property name="geometry">
<rect>
<x>220</x>
<y>100</y>
<width>104</width>
<height>71</height>
</rect>
</property>
</widget>
<widget class="QLabel" name="label">
<property name="geometry">
<rect>
<x>50</x>
<y>120</y>
<width>91</width>
<height>31</height>
</rect>
</property>
<property name="font">
<font>
<pointsize>10</pointsize>
<weight>75</weight>
<bold>true</bold>
</font>
</property>
<property name="text">
<string>Price</string>
</property>
</widget>
<widget class="QSpinBox" name="tax_rate">
<property name="geometry">
<rect>
<x>230</x>
<y>250</y>
<width>42</width>
<height>22</height>
</rect>
</property>
<property name="value">
<number>20</number>
</property>
</widget>
<widget class="QLabel" name="label_2">
<property name="geometry">
<rect>
<x>60</x>
<y>250</y>
<width>47</width>
<height>13</height>
</rect>
</property>
<property name="text">
<string>Tax Rate</string>
</property>
</widget>
<widget class="QPushButton" name="calc_tax_button">
<property name="geometry">
<rect>
<x>230</x>
<y>350</y>
<width>111</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>Calculate Tax</string>
</property>
</widget>
<widget class="QTextEdit" name="results_window">
<property name="geometry">
<rect>
<x>180</x>
<y>410</y>
<width>131</width>
<height>71</height>
</rect>
</property>
</widget>
<widget class="QLabel" name="label_3">
<property name="geometry">
<rect>
<x>170</x>
<y>20</y>
<width>441</width>
<height>41</height>
</rect>
</property>
<property name="font">
<font>
<pointsize>20</pointsize>
<weight>75</weight>
<bold>true</bold>
</font>
</property>
<property name="text">
<string>Sales Tax Calculator</string>
</property>
</widget>
</widget>
<widget class="QMenuBar" name="menubar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>800</width>
<height>20</height>
</rect>
</property>
</widget>
<widget class="QStatusBar" name="statusbar"/>
</widget>
<resources/>
<connections/>
</ui>
See Question&Answers more detail:
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