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Mastering Django: Core

You're reading from   Mastering Django: Core The Complete Guide to Django 1.8 LTS

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Product type Paperback
Published in Dec 2016
Publisher
ISBN-13 9781787281141
Length 694 pages
Edition 1st Edition
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Author (1):
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Nigel George Nigel George
Author Profile Icon Nigel George
Nigel George
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Table of Contents (33) Chapters Close

Mastering Django: Core
Credits
About the Author
www.PacktPub.com
Preface
1. Introduction to Django and Getting Started FREE CHAPTER 2. Views and URLconfs 3. Templates 4. Models 5. The Django Admin Site 6. Forms 7. Advanced Views and URLconfs 8. Advanced Templates 9. Advanced Models 10. Generic Views 11. User Authentication in Django 12. Testing in Django 13. Deploying Django 14. Generating Non-HTML Content 15. Django Sessions 16. Djangos Cache Framework 17. Django Middleware 18. Internationalization 19. Security in Django 20. More on Installing Django 21. Advanced Database Management Model Definition Reference Database API Reference Generic View Reference Settings Built-in Template Tags and Filters Request and Response Objects Developing Django with Visual Studio

Using settings without setting DJANGO_SETTINGS_MODULE


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. Do this by calling:

django.conf.settings.configure(default_settings, **settings) 

Example:

from django.conf import settings 
settings.configure(DEBUG=True, TEMPLATE_DEBUG=True) 

Pass configure() as many keyword arguments as you'd like, with each keyword argument representing a setting and its value. Each argument name should be all uppercase, with the same name as the settings described above. If a particular setting is not passed to configure() and is needed at some later point, Django will use the default setting value.

Configuring Django in this fashion is mostly necessary-and, indeed, recommended-when you're using a piece of the framework inside a larger application. Consequently, when configured via settings.configure(), Django will not make any modifications to the process environment variables (see the documentation of TIME_ZONE for why this would normally occur). It's assumed that you're already in full control of your environment in these cases.

Custom default settings

If you'd like default values to come from somewhere other than django.conf.global_settings, you can pass in a module or class that provides the default settings as the default_settings argument (or as the first positional argument) in the call to configure(). In this example, default settings are taken from myapp_defaults, and the DEBUG setting is set to True, regardless of its value in myapp_defaults:

from django.conf import settings 
from myapp import myapp_defaults 

settings.configure(default_settings=myapp_defaults, DEBUG=True) 

The following example, which uses myapp_defaults as a positional argument, is equivalent:

settings.configure(myapp_defaults, DEBUG=True) 

Normally, you will not need to override the defaults in this fashion. The Django defaults are sufficiently tame that you can safely use them. Be aware that if you do pass in a new default module, it entirely replaces the Django defaults, so you must specify a value for every possible setting that might be used in that code you are importing. Check in django.conf.settings.global_settings for the full list.

Either configure() or DJANGO_SETTINGS_MODULE is required

If you're not setting the DJANGO_SETTINGS_MODULE environment variable, you must call configure() at some point before using any code that reads settings. If you don't set DJANGO_SETTINGS_MODULE and don't call configure(), Django will raise an ImportError exception the first time a setting is accessed. If you set DJANGO_SETTINGS_MODULE, access settings values somehow, then call configure(), Django will raise a RuntimeError indicating that settings have already been configured. There is a property just for this purpose:

django.conf.settings.configured 

For example:

from django.conf import settings 
if not settings.configured:
     settings.configure(myapp_defaults, DEBUG=True) 

Also, it's an error to call configure() more than once, or to call configure() after any setting has been accessed. It boils down to this: Use exactly one of either configure() or DJANGO_SETTINGS_MODULE. Not both, and not neither.

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