I have a script which has a global variable that must be set by the user once and for all, the variable is a string containing a pathname, and each time the script runs it needs it. I don't want to prompt the user each time for this pathname.
Currently, I am considering asking the user to a set an environment variable permanently, by adding it to his /etc/profile or .bash_profile, and access it with sys.environ dictionary. The other option would be to have a config file and ask the user to edit the relevant line, then use configparser to read it.
Is there a recommended method for doing this?
Use the Python ConfigParser module, or configparser in Python 3.
It follows the standard *.ini format and allows you to store information from one run to the next in an easily readable format. The format is essentially self-documenting because you can name your keys in the file, and you can add comments to the configuration file too.
It also provides more flexibility over the environment variable method because it is easier to modify a configuration file, and the file can easily be passed from one computer to the next along with your script regardless of platform or other environment settings.
Your use case is exactly what configuration files are intended for, and you could accomplish your task with only a handful of lines of code:
cfg_parser = ConfigParser.ConfigParser() # Python 2.x
if cfg_parser.read('config_file_name.ini'):
path = cfg_parser.get('SECTION_NAME', 'path')
else:
print("No config file found")
This gives you your path, and all you have to ask your user to do is edit one line of a text file instead of making any system changes.
Additionally, this gives you a lot of room to expand in the future. If you ever want more options added to your script, modifying a configuration file is a lot easier than coming up with new environment variables.
Lastly, the ConfigParser library allows you to edit configuration files programmatically as well. You could add a command line option (perhaps with argparse) that allows your user to specify a path, and have your script automagically write its own config file with the path. Now your user never has to touch the configuration file manually, and will never have to add the path on the command line again either. Even better, if the path ever changes, your user can just run it with the command line path option again and voila, the old path in the config file is overwritten and the new one is saved.
I would definitely recommend the configuration file approach due to its flexibility and user-friendliness.
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