Logging module stopped working!

[llanitedave]

I'm building an application that contains some long-running operations in a separate thread from the user interface.  I've been using the logging module writing logging.info() statements to a .log file to keep track of the data interactions while it runs.

In the midst of a recent run, the logging simply stopped working.  The rest of the application continued on as if nothing had happened, but without the log I'm pretty much blind.

I set up the logging code at the very beginning of the app, before any other work is done.  Here's the relevant code:

#!/usr/bin/env python3 import sys import os #import functions_classes from PyQt5 import QtGui, QtCore, QtWidgets from PyQt5.QtGui import * from PyQt5.QtCore import * from PyQt5.QtWidgets import * import sqlite3 import logging import inspect import threading import datetime #import local modules import qt_EnvTabs import globalnames import evocontrol import inputoutput class MainWindow(QMainWindow):     def __init__(self):         super().__init__()         # set up logging         logging.basicConfig(format='%(levelname)s:%(message)s', filename="sample.log", level=logging.DEBUG)         logging.info("Starting system, MainWindow.__init__,  %s", str(datetime.datetime.today()))         self.createUI()

I also have an earlier draft of the application that I saved into another directory.  Its initial code is identical to what I posted here.  I opened it, saw the first window activate, and then closed it.  I checked for the sample.log file, it existed, and contained the proper message:

"INFO:Starting system, MainWindow.__init__,  2017-10-16 20:58:40.988035"

I did the same to the current file, and no log file was created at all!

Between the time that the logging was working and the time it quit, the only changes I made were to add a couple of logging.info() statements into a downstream module.  But that seems irrelevant here, as those modules aren't included in the above test.

Is there any behind-the-scenes behavior that I'm missing?  I'm stumped.

[llanitedave]

For anyone who read the above post and also didn't know a solution, I now understand it better.  The truth is that "downstream modules" really aren't so downstream after all.  The modules I imported prior to MainWindow() being called all get parsed to at least some extent, and in one of those local modules I had a call to logging.info() that was placed prior to the __init__() function of a class.  The parser apparently tried to process it, but because the configuration command for logging does't get called until I'm in MainWindow.__init__(), it couldn't do anything with it.  I wish this kind of thing wasn't a silent failure, but it is.

The solution was to move the import logging command to higher up in the list, and follow it immediately with the logging.basicConfig() command before any of the local modules get imported.

That gives you a lot more flexibility on where to place your other calls to the logging module.