第二步:Mac Docker创建第一个Django 应用,Part 2
原文:Writing your first Django app, part 2
本文Python搭建在 Django Compose + Djang 执行Python需进入web server容器中,请参看[第一步:在Mac构建Django 容器]
翻译整理:CK
Part 2:配置后端
1. 配置数据库
已有建有的项目为mysite,Docker Django 的教程里建立了一个composeexample,这里不适用它。假设我们的真实项目为mysite,打开myiste/settings.py,默认配置的数据库是SQLite,SQLite包含在Python里,无需安装任何其他东西。如果第一次创建真实的项目,仍然希望用可伸缩性更强的数据库像PostgreSQL,免得将来又要切换数据库则:
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'HOST': 'db',
'PORT': 5432,
}
}
其他数据库绑定参考:Database Bindings
由于使用了Docker容器来运行python,数据迁移$ python manage.py migrate
也需要在容器里做,所以先查看容器
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
bf1ef3b74f1b mysite_web "python3 manage.py..." About an hour ago Up 13 minutes 0.0.0.0:8000->8000/tcp mysite_web_1
09f6cebc8741 postgres "docker-entrypoint..." 2 hours ago Up 13 minutes 5432/tcp mysite_db_1
进入容器并执行migrate:
docker exec -it mysite_db_1 bash
$ python manage.py migrate
这条命令根据myiste/settings.py里的 INSTALLED_APPS 的需要安装必要数据库表格,安装完成后再连接PostgreSQL psql DBNAME USERNAME
root@09f6cebc8741:/# psql postgres postgres
输入\dt
应该能看到类似Tables
postgres=# \dt
List of relations
Schema | Name | Type | Owner
--------+----------------------------+-------+----------
public | auth_group | table | postgres
public | auth_group_permissions | table | postgres
public | auth_permission | table | postgres
public | auth_user | table | postgres
public | auth_user_groups | table | postgres
public | auth_user_user_permissions | table | postgres
public | django_admin_log | table | postgres
public | django_content_type | table | postgres
public | django_migrations | table | postgres
public | django_session | table | postgres
(10 rows)
退出Postgres
postgres-# \q
2. 创建数据模型
编辑polls/models.py
from django.db import models
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
class Choice(models.Model):
question = models.ForeignKey(Question, on_delete=models.CASCADE)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
3. 启动数据模型
-
通知Prject,polls app 应用已安装
编辑mysite/settings.py,添加一行`'polls.apps.PollsConfig',`
INSTALLED_APPS = [
'polls.apps.PollsConfig',
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
]
- 到web容器中执行命令:
$ python manage.py makemigrations polls
makemigrations 告诉Django你对模型做了些修改,并并希望保存下来。Django会创建修改脚本polls/migrations/0001_initial.py,
应该会看到类似:
Migrations for 'polls':
polls/migrations/0001_initial.py:
- Create model Choice
- Create model Question
- Add field question to choice
到此数据库并未改变,真正执行变更并且帮助你管理数据库模式是migration
命令,可以用如下命令查看将要执行的SQL命令
$ python manage.py sqlmigrate polls 0001
应该会看到类似(不同数据库会有所不同):
BEGIN;
--
-- Create model Choice
--
CREATE TABLE "polls_choice" ("id" serial NOT NULL PRIMARY KEY, "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL);
--
-- Create model Question
--
CREATE TABLE "polls_question" ("id" serial NOT NULL PRIMARY KEY, "question_text" varchar(200) NOT NULL, "pub_date" timestamp with time zone NOT NULL);
--
-- Add field question to choice
--
ALTER TABLE "polls_choice" ADD COLUMN "question_id" integer NOT NULL;
CREATE INDEX "polls_choice_question_id_c5b4b260" ON "polls_choice" ("question_id");
ALTER TABLE "polls_choice" ADD CONSTRAINT "polls_choice_question_id_c5b4b260_fk_polls_question_id" FOREIGN KEY ("question_id") REFERENCES "polls_question" ("id") DEFERRABLE INITIALLY DEFERRED;
COMMIT;
保存数据库修改:
$ python manage.py migrate
Operations to perform:
Apply all migrations: admin, auth, contenttypes, polls, sessions
Running migrations:
Rendering model states... DONE
Applying polls.0001_initial... OK
小结:
修改数据库分三步:
- 修改模型 (in models.py).
- 执行:
python manage.py makemigrations
创建一个迁移 - 执行:
python manage.py migrate
保存变更
4. API
下面进入交互式的Python Shell跟API一起玩耍吧,别忘了先进入容器。
$ python manage.py shell
如需了解database API的相关内容:database API
可进行一下尝试了解API:
>>> from polls.models import Question, Choice # 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. Note that this might say "1L" instead of "1", depending
# on which database you're using. That's no biggie; it just means your
# database backend prefers to return integers as Python long integer
# objects.
>>> 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>]>
为了让<Question: Question object>
输出更可读
给模块Question and Choice (in the polls/models.py file) 添加 __str__()
方法
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
@python_2_unicode_compatible # only if you need to support Python 2
class Question(models.Model):
# ...
def __str__(self):
return self.question_text
@python_2_unicode_compatible # only if you need to support Python 2
class Choice(models.Model):
# ...
def __str__(self):
return self.choice_text
除了那些常见的Python方法,可以添加一个自定义的
import datetime
from django.db import models
from django.utils import timezone
class Question(models.Model):
# ...
def was_published_recently(self):
return self.pub_date >= timezone.now() - datetime.timedelta(days=1)
在次进入shell看看有哪些变化:
>>> from polls.models import Question, Choice
# Make sure our __str__() addition worked.
>>> Question.objects.all()
<QuerySet [<Question: What's up?>]>
# Django provides a rich database lookup API that's entirely driven by
# keyword arguments.
>>> Question.objects.filter(id=1)
<QuerySet [<Question: What's up?>]>
>>> Question.objects.filter(question_text__startswith='What')
<QuerySet [<Question: What's up?>]>
# Get the question that was published this year.
>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Question.objects.get(pub_date__year=current_year)
<Question: What's up?>
# Request an ID that doesn't exist, this will raise an exception.
>>> Question.objects.get(id=2)
Traceback (most recent call last):
...
DoesNotExist: Question matching query does not exist.
# Lookup by a primary key is the most common case, so Django provides a
# shortcut for primary-key exact lookups.
# The following is identical to Question.objects.get(id=1).
>>> Question.objects.get(pk=1)
<Question: What's up?>
# Make sure our custom method worked.
>>> q = Question.objects.get(pk=1)
>>> q.was_published_recently()
True
# Give the Question a couple of Choices. The create call constructs a new
# Choice object, does the INSERT statement, adds the choice to the set
# of available choices and returns the new Choice object. Django creates
# a set to hold the "other side" of a ForeignKey relation
# (e.g. a question's choice) which can be accessed via the API.
>>> q = Question.objects.get(pk=1)
# Display any choices from the related object set -- none so far.
>>> q.choice_set.all()
<QuerySet []>
# Create three choices.
>>> q.choice_set.create(choice_text='Not much', votes=0)
<Choice: Not much>
>>> q.choice_set.create(choice_text='The sky', votes=0)
<Choice: The sky>
>>> c = q.choice_set.create(choice_text='Just hacking again', votes=0)
# Choice objects have API access to their related Question objects.
>>> c.question
<Question: What's up?>
# And vice versa: Question objects get access to Choice objects.
>>> q.choice_set.all()
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
>>> q.choice_set.count()
3
# The API automatically follows relationships as far as you need.
# Use double underscores to separate relationships.
# This works as many levels deep as you want; there's no limit.
# Find all Choices for any question whose pub_date is in this year
# (reusing the 'current_year' variable we created above).
>>> Choice.objects.filter(question__pub_date__year=current_year)
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
# Let's delete one of the choices. Use delete() for that.
>>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
>>> c.delete()
5. 介绍Django Admin
1. 创建Admin用户
$ python manage.py createsuperuser
Username: admin
Email address: admin@example.com
验证两次密码:
Password: **********
Password (again): *********
Superuser created successfully.
注册成功
2. 开始服务器开发
Django的Admin是默认激活的
启动服务器 docker-compose up
打开: http://127.0.0.1:8000/admin/
输入账号密码
3. 通过admin来管理poll应用
修改polls/admin.py 注册Question到admin site 来告诉admin Question 已经提供了admin的接口
from django.contrib import admin
from .models import Question
admin.site.register(Question)
可以看到之前创建的question
可以修改
如果选择时间Now的时候发现时间不对,那可能就是时区问题。
检查之前的设置mysite/setting.py
例如:
#TIME_ZONE = 'UTC'
TIME_ZONE = 'Pacific/Auckland'
好了,完成第二步了
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