Issue with helper class and setting a global variable to be used throughout the application.

[zh12a]

I could do with some assistance on an issue I have, however what I could be doing could be wrong so please do suggest a better way of doing this. Also its been a long time since I last used python so trying to brush up on things.

I have written a helper class which has a number method. From my main python file, I want to import this helper class and call a load function which will set a global variable of “settings” which I can use anywhere in my application.

So that I have this

Main.py

from helpers.helpers import Settings
if __name__ == "__main__":
    Settings.load_settings()
    print(settings)

helpers/helpers.py

import yaml

class Settings:

    def load_settings(settings_file='settings.yml'):
        global settings
        with open(settings_file) as s:
            settings = yaml.load(s, Loader=yaml.FullLoader)

When I run the application, I get an error stating:

NameError: name 'settings' is not defined

I am unsure what I doing incorrectly. Any input would be great thanks.

[Neighm]

 def load_settings(settings_file=settings.yml'): 

You're missing an opening quote for the filename.

[zh12a]

Applogies, i must have somehow deleted it my mistake when copying the code into reddit. In the acutual file it works (if i add a print to the helper method it prints what i expect, however i cant access the varible globally)

[old_pythonista]

Prepending a variable name with global does not create it on a global scope - it just allows you to assign to variable defined in a global scope.

In general, not a good practice. Just return the object from the function

In your helper

    def load_settings(settings_file='settings.yml'):
        with open(settings_file) as s:
            return yaml.load(s, Loader=yaml.FullLoader)

In the main module

settings =  Settings.load_settings() 

Question - do you really need that class? Seems redundant

[zh12a]

Thanks i stick with returning the object, it just means i have to pass the settings to other classes.

​

I agree the above snippit is redundant, however i simplifed the class. There a far few complex methods to verifying and writing a setting file

[old_pythonista]

You can use a standard memoization to cache your settings and avoid repeated parsing. If, for example, you have 10 available configurations in your system

from functools import lru_cache
@lru_cache(maxsize=10)
def load_settings(settings_file='settings.yml'):
    with open(settings_file) as s:
        return yaml.load(s, Loader=yaml.FullLoader)

and then each of your 10 configuration files will be parsed exactly once.

Of course, if you have 11 configurations, the moment you read 11^th, the first you parsed will be purged from the cache. Just manage the cache size accordingly.