Referring to an attribute in an MDI application

Question

I'm just learning about tabbed views and MDI in PyQt. I'm confused how I would refer to a line-edit widget that is on one of the tabs. When I look at the object inspector I see:

MainWindow
  centralwidget
    mdiArea
     subwindow
      gridlayout
        wt1

I wish to refer to wt1 in code. How do I do this?

I'm getting the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\218003107\AppData\Local\Continuum\Anaconda\lib\site-  packages\spyderlib\widgets\externalshell\sitecustomize.py", line 580, in runfile
  execfile(filename, namespace)
  File "C:/Users/218003107/callphreeqcInput.pyw", line 38, in <module>
    myapp=MyForm()
  File "C:/Users/218003107/callphreeqcInput.pyw", line 10, in __init__
    self.connect(self.ui.wt1,QtCore.SIGNAL('textChanged()'),self.wtResult)
AttributeError: 'Ui_MainWindow' object has no attribute 'wt1'

My code looks like this:

import sys
from PyQt4 import QtCore, QtGui
from phreqMDI import Ui_MainWindow

class MyForm(QtGui.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        super(MyForm,self).__init__(parent)
        self.ui=Ui_MainWindow()
        self.ui.setupUi(self) 
        self.connect(self.ui.wt1,QtCore.SIGNAL('textChanged()'),self.wtResult)
        self.connect(self.ui.wt2,QtCore.SIGNAL('textChanged()'),self.wtResult)
        self.connect(self.ui.wt3,QtCore.SIGNAL('textChanged()'),self.wtResult)
        self.connect(self.ui.wt4,QtCore.SIGNAL('textChanged()'),self.wtResult)     

    def wtResult(self):
        if len(self.ui.wt1.text())!=0:
            a=float(self.ui.wt1.text())
        else:
            a=0
        if len(self.ui.wt2.text())!=0:
            b=float(self.ui.wt2.text())
        else:
            b=0
        if len(self.ui.wt3.text())!=0:
            c=float(self.ui.wt3.text())
        else:
            c=0
        if len(self.ui.wt4.text())!=0:
            c=float(self.ui.wt4.text())
        else:
            d=0                      
        sum=a+b+c+d
        self.ui.wt_total.setText(str(sum)) 

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    myapp=MyForm()
    myapp.show()
    app.exec_()

Answer 1

The problem is that pyuic does not automatically add the subwindows to the mdi-area. This seems like a bug to me, but I've never used mdi-areas myself, so maybe I'm missing something.

Anyway, you can fix the issue by adding the subwindows yourself, like this:

    self.ui.mdiArea.addSubWindow(self.ui.subwindow)
    self.ui.mdiArea.addSubWindow(self.ui.subwindow_2)

See the QMdiArea docs for more details.

UPDATE:

The reason why the signal connections don't work is because you are using the wrong signature. The is a very common mistake when using the old-style method of connecting signals, so I would advise switching to the new-style method, which would look like this:

    self.ui.wt1.editingFinished.connect(self.wtResult)
    self.ui.wt2.editingFinished.connect(self.wtResult)
    self.ui.wt3.editingFinished.connect(self.wtResult)
    self.ui.wt4.editingFinished.connect(self.wtResult)

Note that I have used the editingFinished signal here, so that only complete entries are evaluated. If you used the textChanged signal, the wtResult method would try to evaluate intermediate entries (e.g. "2."), which would give errors.

You should probably consider setting a validator on your input fields so that only numeric values can be entered.