Debugging

The debugger runs your project (desktop or web) and stops it at the lines you choose in your code: the code generated from the design is not debugged. There is nothing to install: it uses the Python standard library.

1. In the Code tab, click to the left of a line number to set a breakpoint (a red dot); another click removes it. F5 sets it on the cursor line.
2. Right-click the dot to give it a condition (for example qty == 4): it only stops when it is true. It shows a white dot inside.
3. Press Debug (the orange bug, Shift+F9). The program starts and stops when it reaches a breakpoint: the yellow arrow marks the line and the bottom panel opens Variables.

• Variables: the locals and globals of the chosen frame. Lists, dictionaries and objects (such as self) expand to show their state.
• Stack: the chain of calls up to the current line. Clicking a frame chooses it: the variables change and the editor jumps to its line. If it stopped on an error, the full traceback is below.
• Evaluate: type a Python expression (self.total, len(items)) and press Enter. Assignments (n = 5) also work, to change a value before carrying on.
• Breakpoints: every breakpoint with its line and condition; edit or remove them here, and choose when to stop on exceptions: never, on uncaught ones (the default: an error in an event stops at its line) or on all of them, including the ones your code catches with try.

• History: the last lines of your code that ran, with the time and the function. A click takes you to the line.
• Calls: every call to a function of your code and its return, indented by depth and with how long it took: the flow of the program.
• Performance: for every function, how many times it was called and its total, mean and maximum time (not counting debugger pauses), and the most executed lines. It updates by itself; Reset sets the counters to zero.
• Objects: how many live objects there are of each class of your program (and tkinter widgets): handy to see whether something is created too many times.

The Tests tab runs the unittest tests in the project's tests folder (test_*.py files). Create a sample test adds tests/test_form1.py: tests import your program with from dms_app import Form1 (for a web app, from dms_app import app and its test client).

import unittest

from dms_app import Form1


class TestForm1(unittest.TestCase):
    def setUp(self):
        self.form = Form1()
        self.form.root.withdraw()

    def tearDown(self):
        self.form.root.destroy()

    def test_title(self):
        self.assertTrue(self.form.root.title())

Run tests shows every test in green, in red (click it to see its error) or skipped. Debug tests runs them under the debugger: they stop at the breakpoints in your code.