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默认情况下,配置使用SQLite。如果你是数据库新手,或者想尝试学习Django,这是最简单的选择。SQLite包含在Python,所以不需要安装任何东西来支持你的数据库。当开始你的第一个真正的项目,可能需要使用更强大的数据库如:PostgreSQL,MySQL等,可以配置数据库切换就可以了。 如果你想使用其他数据库,请安装相应的数据库绑定,并更改以下键在数据库中“默认”的配置项,以适合您的数据库连接设置: ENGINE – 输入'django.db.backends.sqlite3', 'django.db.backends.postgresql','django.db.backends.mysql',或'django.db.backends.oracle' NAME – 数据库的名称。如果使用SQLite,数据库会在您的计算机上创建文件;在这种情况下,名称应该是完整的绝对路径的文件,包括文件名。默认值为 os.path.join(BASE_DIR,“db.sqlite3”),将存储在您的项目目录中的文件。 如果你不使用SQLite作为数据库,而使用其他设置,如USER, PASSWORD, 和 HOST 必须加入。欲了解更多详细信息,请参阅用于 数据库的参考文档 。 当你编辑 mysite/settings.py,时区设置TIME_ZONE。 此外,请注意,在该文件的顶部的 INSTALLED_APPS 设置。它包含了很多在本Django示例中激活的所有 Django 的应用程序的名称。 应用程序可以在多个项目中使用,你可以打包给别人并在他们的项目分发使用。 默认情况下,INSTALLED_APPS包含以下内容的应用程序,这些都使用 Django : django.contrib.admin – 管理站点,这里会很快使用它 django.contrib.auth – 认证系统 django.contrib.contenttypes – 一个框架,内容类型 django.contrib.sessions – 会话框架 django.contrib.messages – 消息传递框架 django.contrib.staticfiles – 一个框架用来管理静态文件 这些应用包括默认,作为一个方便常见的例子。 其中的一些应用程序使用至少一个数据库表,所以我们需要在数据库中创建的表才可以使用它们。要做到这一点,运行以下命令:
C:\Python27\mysite>python manage.py migrate
Operations to perform:
  Apply all migrations: admin, contenttypes, auth, sessions
Running migrations:
  Rendering model states... DONE
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying sessions.0001_initial... OK
C:\Python27\mysite>
migrate 命令着眼于INSTALLED_APPS设置并创建根据您的 mysite/settings.py 文件数据库设置,并随应用程序数据库迁移任何数据库表(我们将在以后的教程讨论)。你会看到每个适用移植的消息。 如果有兴趣,运行命令行在你的数据库客户端,列如类型\dt (PostgreSQL), SHOW TABLES; (MySQL), .schema (SQLite), 或 SELECT TABLE_NAME FROMUSER_TABLES; (Oracle) 以显示Django所创建的表。 在我们的简单调查的应用程序,我们将创建两个模型:Question 和 Choice。Question有一个问题标题和发布日期。Choice有两个字段:选择文本和票数。每个选项都与一个问题关联。 这些概念由简单的Python类来表示。编辑 polls/models.py 文件,所以 polls/models.py 看起来是这样的:
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)
该代码是直接的。每个模型是django.db.models.Model类的子类。 每个模型具有许多类变量,每一个在模型变量与数据库表的字段关联。 每个字段由 Field 类实例表示 – 例如,CharField表示字符型字段,DateTimeField表示日期时间字段。这告诉Django 每个字段保存的数据类型。 每个Field实例(例如,question_text或pub_date)的名称是字段的名称,这是机器友好的格式。在Python代码中使用这个值,数据库将使用它作为列名。 字段也可以有不同的可选参数;在本示例中,我们已经将票数的默认值设置为0。 最后,需要注意的是关系的定义,这里使用了外键。这告诉 Django 每个选项关联一个问题。 Django支持所有常见的数据库关系:多对一,多对多以及一对之一。 现在Django知道 polls 投票程序。让我们运行另一个命令:
C:\Python27\mysite>python manage.py makemigrations polls
Migrations for 'polls':
  0001_initial.py:
    - Create model Choice
    - Create model Question
    - Add field question to choice
C:\Python27\mysite>
迁移是Django怎么存储您更改的模型(由你的数据库架构决定)- 它们只是在磁盘上的文件。您如果喜欢可以读取移植新的模型,它在文件 polls/migrations/0001_initial.py。你不会希望Django每一次都读取它们,不过将它们设计成人可编辑的,你要知道Django是如何变化的并手动调整。 还有将运行migrations,自动管理数据库模式(表)命令 - 这就是所谓的迁移,让我们看看SQL了解移植运行。 sqlmigrate 命令将移植名称返回SQL显示:
$ python manage.py sqlmigrate polls 0001
应该看到类似下面的东西(我们已经重新格式化它的可读性):
C:\Python27\mysite>python manage.py sqlmigrate polls 0001
BEGIN;
-- Create model Choice
CREATE TABLE "polls_choice" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "c
hoice_text" varchar(200) NOT NULL, "votes" integer NOT NULL);
-- Create model Question
CREATE TABLE "polls_question" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT,
"question_text" varchar(200) NOT NULL, "pub_date" datetime NOT NULL);
-- Add field question to choice
ALTER TABLE "polls_choice" RENAME TO "polls_choice__old";
CREATE TABLE "polls_choice" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "c
hoice_text" varchar(200) NOT NULL, "votes" integer NOT NULL, "question_id" integ
er NOT NULL REFERENCES "polls_question" ("id"));
INSERT INTO "polls_choice" ("choice_text", "votes", "id", "question_id") SELECT
"choice_text", "votes", "id", NULL FROM "polls_choice__old";
DROP TABLE "polls_choice__old";
CREATE INDEX "polls_choice_7aa0f6ee" ON "polls_choice" ("question_id");
COMMIT;
C:\Python27\mysite>
现在,让我们进入交互式 Python shell  和 Django 所提供的API 。要调用Python命令行,请使用以下命令:
C:\Python27\mysite>python manage.py shell
Python 2.7.10 (default, May 23 2015, 09:44:00) [MSC v.1500 64 bit (AMD64)] on wi
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
		只需键入“python” 来代替,因为manage.py设置DJANGO_SETTINGS_MODULE环境变量,这给Django Python 导入路径到 mysite/settings.py文件。
>>> import django
>>> django.setup()
>>> from polls.models import Question, Choice   # Import the model classes we just wrote.
# No questions are in the system yet.
>>> Question.objects.all()
# 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.
# 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()
[<Question: Question object>]
这里需要等待一会儿. <Question: Question object>完全是这个对象的无用表示。让我们来解决这个问题:通过编辑Question模型(在polls/models.py 文件),并添加一个__str__() 方法到这两个Question 和 Choice 模型:polls/models.py文件内容如下:
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
注意这里增加 import datetime 和from django.utils import timezon,引用Python的标准的datetime模块和Django的时区相关的实用程序在django.utils.timezone,如果不熟悉在Python的时区处理,可以阅读时区支持文档。 保存这些修改,并再次运行 python manage.py shell 启动一个新的Python交互shell:
>>> from polls.models import Question, Choice
# Make sure our __str__() addition worked.
>>> Question.objects.all()
[<Question: What's up?>]
# Django provides a rich database lookup API that's entirely driven by
# keyword arguments.
>>> Question.objects.filter(id=1)
[<Question: What's up?>]
>>> Question.objects.filter(question_text__startswith='What')
[<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()
# 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()
# 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()
[<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]
>>> q.choice_set.count()
# 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)
[<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()
介绍 Django管理 修改“Date published”点击“Today”和“Now”快捷方式。然后点击“Save and continue editing.”,然后点击“History”在右上角。你会看到一个页面,列出通过Django管理到这个对象的所有变化,修改人用户名和时间戳:
代码下载:http://pan.baidu.com/s/1jGR3wDg