Part2 , Poll Project

1.-The path() function is passed four arguments, two required: route and view, and two optional: kwargs, and name. 

route is a string that contains a URL pattern. When processing a request, Django starts at the first pattern in urlpatterns and makes its way down the list, comparing the requested URL against each pattern until it finds one that matches.

Patterns don’t search GET and POST parameters, or the domain name. For example, in a request to https://www.mysite.com/myapp/, the URLconf will look for myapp/. In a request to https://www.mysite.com/myapp/?page=5, the URLconf will also look for myapp/.

path() argument: view

When Django finds a matching pattern, it calls the specified view function with an HttpRequest 

path() argument: name

Naming your URL lets you refer to it unambiguously from elsewhere in Django, especially from within templates. This powerful feature allows you to make global changes to the URL patterns of your project while only touching a single file.

2.- Fill the time zone, to your convinience

Some of these applications make use of at least one database table, though, so we need to create the tables in the database before we can use them. To do that, run the following command:

We are going to run this command on the terminal

py manage.py migrate

This is the final result

The migrate command looks at the INSTALLED_APPS setting and creates any necessary database tables according to the database settings in your mysite/settings.py file and the database migrations shipped with the app
Let's run another program py manage.py makemigrations polls

By running makemigrations, you’re telling Django that you’ve made some changes to your models (in this case, you’ve made new ones) and that you’d like the changes to be stored as a migration.
You can see the changes here: polls/migrations/0001_initial.py.

We are not expecting to do anything with this but you can tweak this in the future
There’s a command that will run the migrations for you and manage your database schema automatically - that’s called migrate, and we’ll come to it in a moment - but first, let’s see what SQL that migration would run. The sqlmigrate command takes migration names and returns their SQL:
py manage.py sqlmigrate polls 0001

Notes:  

• The exact output will vary depending on the database you are using. 
• Table names are automatically generated by combining the name of the app (polls) and the lowercase name of the model – question and choice. (You can override this behavior.)
• Primary keys (IDs) are added automatically. (You can override this, too.)
• By convention, Django appends "_id" to the foreign key field name. (Yes, you can override this, as well.)
• The foreign key relationship is made explicit by a FOREIGN KEY constraint. Don’t worry about the DEFERRABLE parts
• It’s tailored to the database you’re using, so database-specific field types such as auto_increment (MySQL), serial (PostgreSQL), or integer primary key autoincrement (SQLite) are handled for you automatically. Same goes for the quoting of field names – e.g., using double quotes or single quotes.
• The sqlmigrate command doesn’t actually run the migration on your database - it just prints it to the screen so that you can see what SQL Django thinks is required. It’s useful for checking what Django is going to do or if you have database administrators who require SQL scripts for changes.

If you’re interested, you can also run python manage.py check; this checks for any problems in your project without making migrations or touching the database.

Now, run migrate again to create those model tables in your database:

The migrate command takes all the migrations that haven’t been applied (Django tracks which ones are applied using a special table in your database called django_migrations) and runs them against your database - essentially, synchronizing the changes you made to your models with the schema in the database.

Migrations are very powerful and let you change your models over time, as you develop your project, without the need to delete your database or tables and make new ones - it specializes in upgrading your database live, without losing data

three-step guide to making model changes:

• Change your models (in models.py).
• Run python manage.py makemigrations to create migrations for those changes
• Run python manage.py migrate to apply those changes to the database.