In the previous section, we added an application to the project , Now add a database to it to interact with the database .
Django By default, there is a lightweight database called SQLite, When we want to change other databases , You need to bind the database , How to bind ？ First, open the project's settings.py, Find the inside DATABASES, The inside engine、name、password It is OK to change the data information to be connected . This is the basic method of binding database and project .
Models Let's create the model ：
The model mentioned above is actually the layout of the database , That is to design those databases , So what models are there . Let's go over it again ：Models The classes inside are tables , Properties are fields （ Name ), An object of a class is a row of a table . Every one created Models All are Django.db.models.Model Subclasses of , That is to say, every model All inherited from models.Model, And every attribute （ Field ） All are Field Real series of . as follows ：
from django.db import models
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')The above is how to use the model database and model in the project . It seems quite simple ~~~ It doesn't seem difficult ~~~
Here we will have a database and model , With the model , How do we use this model ？ That is, we use the tables in the database , How to add, delete, modify and query this table ？
open pycharm, Enter command line mode , Import the module of the project , like this ：
>>> from polls.models import Choice, Question # Import the model classes we just wrote. # No questions are in the system yet. >>> Question.objects.all() <QuerySet []> # Create a new Question. # Support for time zones is enabled in the default settings file, so # Django expects a datetime with tzinfo for pub_date. Use timezone.now() # instead of datetime.datetime.now() and it will do the right thing. >>> from django.utils import timezone >>> q = Question(question_text="What's new?", pub_date=timezone.now()) # Save the object into the database. You have to call save() explicitly. >>> q.save() # Now it has an ID. >>> q.id 1 # Access model field values via Python attributes. >>> q.question_text "What's new?" >>> q.pub_date datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>) # Change values by changing the attributes, then calling save(). >>> q.question_text = "What's up?" >>> q.save() # objects.all() displays all the questions in the database. >>> Question.objects.all() <QuerySet [<Question: Question object (1)>]>
The above is the operation of the data in the table . wait a minute , Here is another important point ： When I want to print an object , This is the address of the printed object ： It is not the specific data of the object we want , How to deal with this problem ？ We were right models When the design , Add one more inside __str__() The method is ok . like this ：
class Question(models.Model): # ... def __str__(self): return self.question_text
When we print objects again , Is to print out the data of specific objects .
