What does os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'folder.settings') do?

Question

I am taking an online Django class now, and I don't understand some of the configuration code. My instructor says that the following code is required in a Python code that populates my database.

import os os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'ProTwo.settings')  import django django.setup() 

I don't understand what this code is doing at all, except that the second argument in setdefault() is referring to my app's settings.py file.

What is DJANGO_SETTINGS_MODULE? What does it do? Why is it passed in as an arg in setdefault()?

And what does django.setup() do? What does it change?

Answer 1

First look at os.environ.setdefault(), environ is an instance of class _Environ, which inherits from IterableUserDict, and IterableUserDict inherits from UserDict, including setdefault().

This method is also a method of UserDict, take a look at the functions implemented by setdefault.

def setdefault(self, key, failobj=None): if key not in self:     self[key] = failobj return self[key] 

The key is DJANGO_SETTINGS_MODULE, where self is a dictionary to determine if the key is inside, and do a key-value binding if it is not inside. Then return.

And here is the original link： Django搭建及源码分析(二)

Answer 2

In some cases, you might want to bypass the DJANGO_SETTINGS_MODULE environment variable. For example, if you’re using the template system by itself, you likely don’t want to have to set up an environment variable pointing to a settings module.

In these cases, you can configure Django’s settings manually.

https://docs.djangoproject.com/en/2.1/topics/settings/