Neither pdb or print() displays the bug

[Rich Shepard]

On Sun, 30 May 2021, Cameron Simpson wrote:

> I've only just started with pdb. As of Python 3.7 there's a builtin
> function named breakpoint() which drops you into the debugger. I've never
> been a big debugger person, historicly using print() and equivalent.
> However, this makes it very easy to insert this call into a piece of code
> instead of having to invoke one's programme in a special way.

I'm stuck with neither approach (pdb, print()) working. I moved the database
code to a separate module, datasource.py, and when I run the
activitytypes.py module (using pdb and having entered print() statements at
various places in both the datasource and activities modules all I get is a
small, empty window with the window title. The QSize() statement is never
reached.

The activitytypes.py module:

import sys
from PyQt5 import QtWidgets as qtw
from PyQt5 import QtGui as qtg
from PyQt5 import QtCore as qtc
from PyQt5 import QtSql as qts

from datasource import db

class ATMainWindow(qtw.QMainWindow):

     def __init__(self):
         super().__init__()

         # Model/View here.
         self.model = qts.QSqlTableModel(db=db) # for single table
         self.model.setTable('activitytypes')
         self.model.select()

         self.table = qtw.QTableView()
         self.table.setModel(self.model)

         self.setFixedSize(qtc.QSize(800, 600))
         self.setCentralWidget(self.table)


if __name__ == '__main__':
     app = qtw.QApplication(sys.argv)
     window = ATMainWindow()
     window.show()
     #sys.exit(app.exec())
     app.exec_()

Running the module in pdb and using 'next' to step through it produces this
result:

> $/development/business_tracker/activitytypes.py(29)<module>()
-> window = ATMainWindow()
(Pdb) n
False
> $/development/business_tracker/activitytypes.py(30)<module>()
-> window.show()
(Pdb) n
> $/development/business_tracker/activitytypes.py(32)<module>()
-> app.exec_()
(Pdb) n
n
> $/development/business_tracker/activitytypes.py(32)<module>()->None
-> app.exec_()
(Pdb) n

and there it sits. No (Pdb) prompt, nothing. And no printed statements.

I'd appreciate recommendations on the process to find where the bug lives
since I can't seem to find it with print() or line-by-line in pdb.

TIA,

Rich