Passing global variables to function in PyQt5

Question

I am creating the application, that requires typing some values from the screen keypad. I've already got buttons with numbers calling the function, that should update the number I would like to use. But every time the button is pressed a different decimal position should be filled. So I need two global variables: one for current number and other for current decimal position. But I don't know, where to put the definition of these two variables, so they were considered as globals and were able to be used inside of any function. My code looks as follows:

import sys
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QApplication, QFileDialog, QMessageBox
from PyQt5.QtCore import QTimer
from mainwindow import Ui_MainWindow


class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
   def __init__(self, *args, obj=None, **kwargs):
      super(MainWindow, self).__init__(*args, **kwargs)
      self.setupUi(self)
      self.kpadBtn0.clicked.connect(lambda:self.setValue(0))
      self.kpadBtn1.clicked.connect(lambda:self.setValue(1))
      self.kpadBtn2.clicked.connect(lambda:self.setValue(2))
      self.kpadBtn3.clicked.connect(lambda:self.setValue(3))
      self.kpadBtn4.clicked.connect(lambda:self.setValue(4))
      self.kpadBtn5.clicked.connect(lambda:self.setValue(5))
      self.kpadBtn6.clicked.connect(lambda:self.setValue(6))
      self.kpadBtn7.clicked.connect(lambda:self.setValue(7))
      self.kpadBtn8.clicked.connect(lambda:self.setValue(8))
      self.kpadBtn9.clicked.connect(lambda:self.setValue(9))

   disp_pos=1  #here it does not work
   val=0

   def setValue(self,num):
      val+=num*disp_pos   #it should be usable here
      disp_pos*=10
      self.newPosDisplay.setText(str(val))

app = QtWidgets.QApplication(sys.argv)

window = MainWindow()
window.show()
app.exec()

When I press button the following error is shown:

NameError: name 'val' is not defined

score 3 · Accepted Answer · answered Feb 23 '20 at 08:13

Use the global variables as a last option since the abuse of them brings problems as indicated in Why are global variables evil?. In your case it is enough that dispos_pos and val are attributes of the class:

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self, *args, obj=None, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        self.setupUi(self)

        self.disp_pos = 1
        self.val = 0

        self.kpadBtn0.clicked.connect(lambda: self.setValue(0))
        self.kpadBtn1.clicked.connect(lambda: self.setValue(1))
        self.kpadBtn2.clicked.connect(lambda: self.setValue(2))
        self.kpadBtn3.clicked.connect(lambda: self.setValue(3))
        self.kpadBtn4.clicked.connect(lambda: self.setValue(4))
        self.kpadBtn5.clicked.connect(lambda: self.setValue(5))
        self.kpadBtn6.clicked.connect(lambda: self.setValue(6))
        self.kpadBtn7.clicked.connect(lambda: self.setValue(7))
        self.kpadBtn8.clicked.connect(lambda: self.setValue(8))
        self.kpadBtn9.clicked.connect(lambda: self.setValue(9))

    def setValue(self, num):
        self.val += num * self.disp_pos
        self.disp_pos *= 10
        self.newPosDisplay.setText(str(self.val))

Passing global variables to function in PyQt5

1 Answers1