Django学习笔记之一

一、Windows下安装　Django

１、下载安装包解压后放到本地目录如C:\Django-1.7.2　官网地址：https://www.djangoproject.com/download/　

２、打开命令行，输入 cd C:\Django-1.7.2　然后定位到当前目录

３、输入　python setup.py　install　开始安装

４、配置各种环境变量，C:\Python34\;C:\Python34\Scripts;C:\Python34\Lib\site-packages\Django-1.7.2-py3.4.egg\django;

５、验证是否安装成功

D:\project\mysite>python
>>> import django
>>> print(django.get_version())
1.7.2

安装成功！

二、通过官网的简单投票系统学习使用[https://docs.djangoproject.com/en/1.7/intro/tutorial01/]

１、创建一个项目，先在命令行cd　到想要创建项目所在的目录如D:\project\，然后输入如下命令

django-admin.py startproject mysite

此时已经自动创建了如下目录

mysite/
    manage.py
    mysite/
        __init__.py
        settings.py
        urls.py
        wsgi.py

２、使用已经自动安装了的SQLite

python manage.py migrate

３、启动服务器，通过如下网址可以访问网页

python manage.py runserver

Performing system checks...

0 errors found
January 27, 2015 - 15:50:53
Django version 1.7, using settings 'mysite.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

４、在网站下创建一个名叫pools的APP投票应用　

python manage.py startapp polls

被创建的目录如下：
polls/
    __init__.py
    admin.py
    migrations/
        __init__.py
    models.py
    tests.py
    views.py

５、创建Models（ＭＶＣ架构中的model，用于自动生成对应的数据库）

１）打开文件polls/models.py添加如下代码

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)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

２）激活Models

打开配置文件mysite/settings.py，把我们刚创建的pools添加进去

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'polls',
)

２.１）在命令行执行

python manage.py makemigrations polls　　#这是第一步，创建对Model的修改，可以打开polls/migrations/0001_initial.py文件查看代码格式

Migrations for 'polls':
  0001_initial.py:
    - Create model Question
    - Create model Choice
    - Add field question to choice

或者输入：python manage.py sqlmigrate polls 0001查看创建了些什么，结果如下：

BEGIN;
CREATE TABLE polls_question (
    "id" serial NOT NULL PRIMARY KEY,
    "question_text" varchar(200) NOT NULL,
    "pub_date" timestamp with time zone NOT NULL
);

CREATE TABLE polls_choice (
    "id" serial NOT NULL PRIMARY KEY,
    "question_id" integer NOT NULL,
    "choice_text" varchar(200) NOT NULL,
    "votes" integer NOT NULL
);

CREATE INDEX polls_choice_7aa0f6ee ON "polls_choice" ("question_id");

ALTER TABLE "polls_choice"
  ADD CONSTRAINT polls_choice_question_id_246c99a640fbbd72_fk_polls_question_id
    FOREIGN KEY ("question_id")
    REFERENCES "polls_question" ("id")
    DEFERRABLE INITIALLY DEFERRED;
COMMIT;

２.２）在命令行执行

python manage.py migrate　　　#这是第二步，应用刚才创建的对Model的修改,sqlLite数据库里面会自动根据Model来修改数据库

Apply all migrations: admin, contenttypes, polls, auth, sessions
Running migrations:
  Applying <migration name>... OK

此时数据库已经创建完了，可以打开python测试一下

>>> from polls.models import Question, Choice

>>> Question.objects.all()

[]

>>> from django.utils import timezone
>>> q = Question(question_text="What's new?", pub_date=timezone.now())

>>> q.save()

>>> q.id

>>> q.question_text
"What's new?"
>>> q.pub_date
datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>)

>>> q.question_text = "What's up?"
>>> q.save()

>>> Question.objects.all()
[<Question: Question object>]

修改polls/models.py

from django.db import models

class Question(models.Model):
    # ...
    def __str__(self):              # __unicode__ on Python 2
        return self.question_text

class Choice(models.Model):
    # ...
    def __str__(self):              # __unicode__ on Python 2
        return self.choice_text
添加自定义函数

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)
再随便玩玩

>>> from polls.models import Question, Choice

# 确保 __str__() 可用.
>>> Question.objects.all()
[<Question: What's up?>]

# Django自带的数据查询 API
>>> Question.objects.filter(id=1)
[<Question: What's up?>]
>>> Question.objects.filter(question_text__startswith='What')
[<Question: What's up?>]

>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Question.objects.get(pub_date__year=current_year)
<Question: What's up?>

>>> Question.objects.get(id=2)
Traceback (most recent call last):
...
DoesNotExist: Question matching query does not exist.

>>> Question.objects.get(pk=1)
<Question: What's up?>

# 确保我们的自定义函数可用.
>>> q = Question.objects.get(pk=1)
>>> q.was_published_recently()
True

>>> q = Question.objects.get(pk=1)

>>> q.choice_set.all()
[]

>>> 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)

>>> c.question
<Question: What's up?>

>>> q.choice_set.all()
[<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]
>>> q.choice_set.count()
3

>>> Choice.objects.filter(question__pub_date__year=current_year)
[<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]

>>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
>>> c.delete()