[PyQt] No reaction and no error message when clicking button

[Atalanttore]

Hi

I have no idea why nothing happens after clicking on "Start Test" in the given Python 3 (PyQt5) code. There appears also no error message.

mainwindow.ui:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117

<?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>350</width>     <height>250</height>    </rect>   </property>   <property name="windowTitle">    <string>Color Concentration Test</string>   </property>   <widget class="QWidget" name="centralwidget">    <layout class="QGridLayout" name="gridLayout_2">     <item row="0" column="0">      <layout class="QVBoxLayout" name="verticalLayout">       <item>        <spacer name="verticalSpacer_2">         <property name="orientation">          <enum>Qt::Vertical</enum>         </property>         <property name="sizeHint" stdset="0">          <size>           <width>20</width>           <height>40</height>          </size>         </property>        </spacer>       </item>       <item>        <widget class="QGroupBox" name="">         <layout class="QGridLayout" name="gridLayout">          <item row="1" column="1">           <widget class="QSpinBox" name="spinBox_switch_time">            <property name="maximum">             <number>100000</number>            </property>            <property name="value">             <number>1000</number>            </property>           </widget>          </item>          <item row="1" column="0">           <widget class="QLabel" name="label_switch_time">            <property name="text">             <string>Switch Time (ms):</string>            </property>            <property name="alignment">             <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>            </property>           </widget>          </item>          <item row="0" column="1">           <widget class="QComboBox" name="comboBox_designated_color">            <property name="currentText">             <string/>            </property>           </widget>          </item>          <item row="0" column="0">           <widget class="QLabel" name="label_designated_color">            <property name="text">             <string>Designated Color:</string>            </property>            <property name="alignment">             <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>            </property>           </widget>          </item>         </layout>        </widget>       </item>       <item>        <spacer name="verticalSpacer">         <property name="orientation">          <enum>Qt::Vertical</enum>         </property>         <property name="sizeHint" stdset="0">          <size>           <width>20</width>           <height>40</height>          </size>         </property>        </spacer>       </item>       <item>        <widget class="QPushButton" name="pushButton_start_test">         <property name="layoutDirection">          <enum>Qt::LeftToRight</enum>         </property>         <property name="text">          <string>Start Test</string>         </property>        </widget>       </item>      </layout>     </item>    </layout>   </widget>   <widget class="QMenuBar" name="menubar">    <property name="geometry">     <rect>      <x>0</x>      <y>0</y>      <width>350</width>      <height>28</height>     </rect>    </property>   </widget>   <widget class="QStatusBar" name="statusbar"/>  </widget>  <resources/>  <connections/> </ui>

main.py:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107

import sys import time from random import choice   from PyQt5.QtWidgets import QApplication, QMainWindow from PyQt5.uic import loadUi from PyQt5 import QtCore     class ConcentrationTest(object):     def __init__(self, COLORS, designated_color):         self.COLORS = COLORS         self.designated_color = designated_color         self.start_time = None         self.color = None         self.color_locked = True         self.reaction_times = []         self.false_positives = 0         self.color_missed = 0         self.key_too_often_pressed = 0       def space_pressed(self):         if self.color == self.designated_color:             if self.color_locked:                 self.key_too_often_pressed += 1             else:                 reaction_time = time.monotonic() - self.start_time                 self.reaction_times.append(reaction_time)                 self.color_locked = True         else:             self.false_positives += 1       def next_round(self):         if not self.color_locked and self.color == self.designated_color:             self.color_missed += 1         self.color_locked = False         current_color = self.color         while self.color == current_color:             self.color = choice(list(self.COLORS.values()))         self.start_time = time.monotonic()         return self.color     class MainWindow(QMainWindow):     COLORS = {"Black": QtCore.Qt.black,         "Blue": QtCore.Qt.blue,         "Cyan": QtCore.Qt.cyan,         "Green": QtCore.Qt.green,         "Magenta": QtCore.Qt.magenta,         "Red": QtCore.Qt.red,         "Yellow": QtCore.Qt.yellow}       def __init__(self, concentration_test, parent=None):         super().__init__(parent)         loadUi("mainwindow.ui", self)         self.concentration_test = concentration_test         self.comboBox_designated_color.addItems(self.COLORS)         self.pushButton_start_test.clicked.connect(self.show_concentration_test_window)       def get_designated_color(self):         return self.COLORS[self.comboBox_designated_color.currentText()]       def get_switch_time(self):         return self.spinBox_switch_time.value()       def show_concentration_test_window(self):         concentration_test = ConcentrationTest(self.COLORS, self.get_designated_color())         concentration_test_window = ConcentrationTestWindow(concentration_test, self.get_switch_time())         concentration_test_window.show()         concentration_test_window.change_screen_color()     class ConcentrationTestWindow(QMainWindow):     def __init__(self, concentration_test, switch_time, parent=None):         super().__init__(parent)         self.showFullScreen()         self.concentration_test = concentration_test         self.switch_time = switch_time         self.timer = QtCore.QTimer()         self.timer.timeout.connect(self.change_screen_color)         self.pal = self.palette()         self.setAutoFillBackground(True)       def change_screen_color(self):         color = self.concentration_test.next_round()         self.pal.setColor(self.backgroundRole(), color)         self.setPalette(self.pal)         self.timer.start(self.switch_time)       def keyPressEvent(self, event):         if event.key() == QtCore.Qt.Key_Escape:             self.close()           if event.key() == QtCore.Qt.Key_Space:             self.concentration_test.space_pressed()       def main():     app = QApplication(sys.argv)     main_window = MainWindow(app)     main_window.show()     sys.exit(app.exec_())     if __name__ == "__main__":     main()

What is the reason for this?

[Alfalfa]

The problem is that your subwindow must be owned by another object, else it is immediatly destroyed by the garbage collector. Therefore, this works (see the 'show_concentration_test_window' method):

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106

#!/usr/bin/python3 import sys import time from random import choice    from PyQt5.QtWidgets import QApplication, QMainWindow from PyQt5.uic import loadUi from PyQt5 import QtCore       class ConcentrationTest(object):     def __init__(self, COLORS, designated_color):         self.COLORS = COLORS         self.designated_color = designated_color         self.start_time = None         self.color = None         self.color_locked = True         self.reaction_times = []         self.false_positives = 0         self.color_missed = 0         self.key_too_often_pressed = 0        def space_pressed(self):         if self.color == self.designated_color:             if self.color_locked:                 self.key_too_often_pressed += 1             else:                 reaction_time = time.monotonic() - self.start_time                 self.reaction_times.append(reaction_time)                 self.color_locked = True         else:             self.false_positives += 1        def next_round(self):         if not self.color_locked and self.color == self.designated_color:             self.color_missed += 1         self.color_locked = False         current_color = self.color         while self.color == current_color:             self.color = choice(list(self.COLORS.values()))         self.start_time = time.monotonic()         return self.color       class MainWindow(QMainWindow):     def __init__(self, parent=None):         super().__init__()         loadUi("mainwindow.ui", self)         self.COLORS = {"Black": QtCore.Qt.black,             "Blue": QtCore.Qt.blue,             "Cyan": QtCore.Qt.cyan,             "Green": QtCore.Qt.green,             "Magenta": QtCore.Qt.magenta,             "Red": QtCore.Qt.red,             "Yellow": QtCore.Qt.yellow}         self.comboBox_designated_color.addItems(self.COLORS)         self.pushButton_start_test.clicked.connect(self.show_concentration_test_window)        def get_designated_color(self):         return self.COLORS[self.comboBox_designated_color.currentText()]        def get_switch_time(self):         return self.spinBox_switch_time.value()        def show_concentration_test_window(self):         self.concentration_test = ConcentrationTest(self.COLORS, self.get_designated_color())         self.concentration_test_window = ConcentrationTestWindow(self.concentration_test, self.get_switch_time())         self.concentration_test_window.show()         self.concentration_test_window.change_screen_color()       class ConcentrationTestWindow(QMainWindow):     def __init__(self, concentration_test, switch_time, parent=None):         super().__init__(parent)         self.showFullScreen()         self.concentration_test = concentration_test         self.switch_time = switch_time         self.timer = QtCore.QTimer()         self.timer.timeout.connect(self.change_screen_color)         self.pal = self.palette()         self.setAutoFillBackground(True)        def change_screen_color(self):         color = self.concentration_test.next_round()         self.pal.setColor(self.backgroundRole(), color)         self.setPalette(self.pal)         self.timer.start(self.switch_time)        def keyPressEvent(self, event):         if event.key() == QtCore.Qt.Key_Escape:             self.close()            if event.key() == QtCore.Qt.Key_Space:             self.concentration_test.space_pressed()          def main():     app = QApplication(sys.argv)     main_window = MainWindow(app)     main_window.show()     sys.exit(app.exec_())       if __name__ == "__main__":     main()

From a quick look, the structure would also need to be reviewed a bit, i.e. why declare concentration_test here

1	def __init__(self, concentration_test, parent=None):

as when you init the MainWindow, only app is passed

1	main_window = MainWindow(app)

[Atalanttore]

Many thanks for fixing the code. I have some questions about your changes:

1. Does your explanation mean that every window instantiated after the main window always needs to be an attribute of another object?

---

'show_concentration_test_window' method before your fixes:

1 2 3 4 5

def show_concentration_test_window(self):     concentration_test = ConcentrationTest(self.COLORS, self.get_designated_color())     concentration_test_window = ConcentrationTestWindow(concentration_test, self.get_switch_time())     concentration_test_window.show()     concentration_test_window.change_screen_color()

'show_concentration_test_window' method after your fixes:

1 2 3 4 5

def show_concentration_test_window(self):     self.concentration_test = ConcentrationTest(self.COLORS, self.get_designated_color())     self.concentration_test_window = ConcentrationTestWindow(self.concentration_test, self.get_switch_time())     self.concentration_test_window.show()     self.concentration_test_window.change_screen_color()

---

'__init__' method of 'MainWindow' class before your fixes:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

class MainWindow(QMainWindow):     COLORS = {"Black": QtCore.Qt.black,               "Blue": QtCore.Qt.blue,               "Cyan": QtCore.Qt.cyan,               "Green": QtCore.Qt.green,               "Magenta": QtCore.Qt.magenta,               "Red": QtCore.Qt.red,               "Yellow": QtCore.Qt.yellow}       def __init__(self, concentration_test, parent=None):         super().__init__(parent)         loadUi("mainwindow.ui", self)         self.concentration_test = concentration_test         self.comboBox_designated_color.addItems(self.COLORS)         self.pushButton_start_test.clicked.connect(self.show_concentration_test_window)

The declaration of 'concentration_test' seems to be a relic from last refactoring.

'__init__' method of 'MainWindow' class after your fixes:

1 2 3 4 5 6 7 8 9 10 11 12 13

class MainWindow(QMainWindow):     def __init__(self, parent=None):         super().__init__()         loadUi("mainwindow.ui", self)         self.COLORS = {"Black": QtCore.Qt.black,                        "Blue": QtCore.Qt.blue,                        "Cyan": QtCore.Qt.cyan,                        "Green": QtCore.Qt.green,                        "Magenta": QtCore.Qt.magenta,                        "Red": QtCore.Qt.red,                        "Yellow": QtCore.Qt.yellow}         self.comboBox_designated_color.addItems(self.COLORS)         self.pushButton_start_test.clicked.connect(self.show_concentration_test_window)

---

2. What's the reason for changing the (constant) class variable 'COLORS' to an object variable 'self.COLORS'?

[Alfalfa]

1. Does your explanation mean that every window instantiated after the main window always needs to be an attribute of another object?

I think that when you have a blocking window, such as:

1 2	msg = QtWidgets.QInputDialog() print(msg.exec_())

You don't need to attribute it to self. In your case, the show() method was not blocking, so the new window is destroyed right after the execution of the method (I could see the window appearing for a fraction of a sec).

2. What's the reason for changing the (constant) class variable 'COLORS' to an object variable 'self.COLORS'?

I just felt that it was weird to see a variable declared there. But to avoid clutter in the top of your class I would rather save this space for declarations that requires it (Qt macros or thread signals). I'm not sure about what the best practice, so it might just be a matter of personnal preferences but I think it make more sense this way.

[Atalanttore]

Thanks for your explanation.