Heroku和本地部署中的Django应用

Question

I have a django app with the following if else block in my settings.py file

if block is getting executed when app runs in heroku , else is getting executed when app is in local system, please explain what is this os.getenviron.get ? and what MBAIR,False is used for?

import os
if not bool(os.environ.get('MBAIR', False)):

 DEBUG = True
    import dj_database_url
    DATABASES = {'default': dj_database_url.config(default='postgres://localhost')}
else:
   DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.postgresql_psycopg2',  
            'NAME': 'rsdfmsfgjsdk_sdfhsdfh'
            'USER': 'sdfhsdfhsdf',
            'PASSWORD': 'sdhsdfhsdhgfsdf', 
            'HOST': 'localhost',
            'PORT': '',  
        }
    }

Answer 1

os.environ.get('MBAIR', False) searches for an environmental variable called MBAIR. If it does not exist, it returns False.

So when you use that if statement, you're searching for an environmental variable that you're assuming is only set on a heroku server. If found, it sets DEBUG to FALSE and then uses dj_database_url.config to create the database configuration dictionary with the following arguments:

DATABASES = {'default': dj_database_url.config(default='postgres://localhost')}

Otherwise it uses your manually defined database settings.

edit: you can try this out like this:

>>> import os
>>> os.environ['testvariable'] = "dookie"
>>> os.environ.get('testvariable', False)
'dookie'
>>> os.environ.get('MBAIR', False)
False
>>> os.environ.get('MBAIR', "Hooha")
'Hooha'

Also, False can be replaced with just about anything.