Python ConfigParser use defaults if not in configuration file

Question

What's the best way to use a default value if it isn't defined in a configuration file? E.g. in the example below, perhaps only listen_address is defined in the configuration, and listen_port is absent.

I'm trying something like this:

import ConfigParser
from os.path import isfile

if __name__ == "__main__":

    # Set default values
    listen_address = '127.0.0.1'
    listen_port = 8000

    # Check for configurations from file and override defaults
    configFile = './configuration.ini'
    if isfile(configFile):
        configs = ConfigParser.ConfigParser()
        configs.read(configFile)
        try:
            listen_address = configs.get('ServerConfigs', 'listen_address')
        except:
            pass
        try:
            listen_port = configs.get('ServerConfigs', 'listen_port')
        except:
            pass

But that feels ugly.

If the parameter is not present in the configuration file, will the attempted assignment result in the variable being unset? I'm not at my computer, so can't test right now. — Rusty Lemur, Feb 28 '19 at 01:46

score 8 · Accepted Answer · answered Apr 20 '19 at 12:53

8

You could use the built-in fallback parameter found here that is used if it cannot find the option:

listen_address = configs.get('ServerConfigs', 'listen_address', fallback='127.0.0.1')

answered Apr 20 '19 at 12:53

L0ngSh0t

361
2
9

I'm keeping this marked as the answer since it was submitted a little before the other one with the same solution. However, I found just now that it is not supported in 2.7. Are there other options for 2.7? – Rusty Lemur May 06 '19 at 19:30
Is there a way to have fallback values when loading from JSON files? Didn't see anything in the docs yet https://docs.python.org/3/library/configparser.html#fallback-values – Nav Jun 21 '23 at 12:53

score 1 · Answer 2 · answered Apr 20 '19 at 13:09

https://docs.python.org/3/library/configparser.html#fallback-values

if __name__ == "__main__":

    # Set default values
    listen_address = '127.0.0.1'
    listen_port = 8000

    # Check for configurations from file and override defaults
    configFile = './configuration.ini'
    if isfile(configFile):
        try:
            configs = ConfigParser.ConfigParser()
            configs.read(configFile)
            listen_address = configs.get('ServerConfigs', 'listen_address', fallback=listen_address)
            listen_port = configs.get('ServerConfigs', 'listen_port', fallback=listen_port)
        except configparser.Error:
            # do whatever u want
            pass

Python ConfigParser use defaults if not in configuration file

2 Answers2

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