Re: FileNotFoundError thrown due to file name in file, rather than file itself

On 12/11/24 10:17, Cameron Simpson via Python-list wrote:

On 11Nov2024 18:24, dieter.maurer@online.de <dieter.maurer@online.de> wrote:

Loris Bennett wrote at 2024-11-11 15:05 +0100:

I have the following in my program:
   try:
       logging.config.fileConfig(args.config_file)
       config = configparser.ConfigParser()
       config.read(args.config_file)
       if args.verbose:
           print(f"Configuration file: {args.config_file}")
   except FileNotFoundError:
       print(f"Error: configuration file {args.config_file} not found.  Exiting.")

>

My questions are:
 1. Should I be surprised by this behaviour?

No. Python has behaved as-programmed.

2. In terms of generating a helpful error message, how should one
  distinguish between the config file not existing and the log file not
  existing?

 Generally you should put a try/except around the smallest possible piece of code. So:
      config = configparser.ConfigParser()
     try:
         config.read(args.config_file)
     except FileNotFoundError as e:
         print(f"Error: configuration file {args.config_file} not found: {e}")
 This way you know that the config file was missing.

Augmenting @Cameron's excellent advice: please research "Separation of Concerns", eg https://en.wikipedia.org/wiki/Separation_of_concerns (which overlaps with one interpretation of SOLID's "Single Responsibility Principle" and the *nix philosophy of "do one thing, and do it well").
If you were to explain the code-snippet in English (or ...) it has several parts/concerns:
- configure the log
- instantiate ConfigParser()
- read the env.file
- advise verbosity-setting
- handle file-error
- (and, but not appearing) terminate execution
A block of code (see indentation for rough definition of "block") should achieve one thing ("concern"). Thus, the advice to separate-out the file-read and attendant defensive-coding.
This anticipates the problem (2) of distinguishing the subject of any one error/stack-trace from any others - and, arguably, makes the code easier to read.
--
Regards,
=dn