开始你的第一个django_part1

学习地址:官网

全英文的，有点困难，现在是边看边写，最后把代码贴上来就可以了。

想偷懒，想了下，还是算了，边学便翻译吧，不对的望大神指教了。

我的操作环境win7+python2.7+django1.6

安装django，这个配置网上一大片，百度一下就可了。

先看下安装成功没有

成功了的。

先来创建一个项目，进入我们的django安装目录

 看见django-admin.py这个文件了吧，在dos下cd进这个目录。

使用python django-admin.py startproject mysite创建一个mysite的项目

目录结构会是下面这个样子的

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

 使用  python manage.py runserver 命令运行开发服务器

 出现如下信息，表明成功了

Validating models...

0 errors found
May 25, 2015 - 15:50:53
Django version 1.6, using settings 'mysite.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

 在浏览器输入上面那个http地址吧，it worked!

端口默认是8000，可以使用 
python manage.py runserver 8080 
python manage.py runserver 0.0.0.0:8000  

 创建我们的应用，投票程序app，其实就是python的一个包而已

使用 python manage.py startapp polls创建

目录结构如下：

polls/
    __init__.py
    admin.py
    models.py
    tests.py
    views.py

 一个投票程序，需要有问题和选项，一个选项有一个描述和一个投票数量

在models.py文件里面配置如下：

from django.db import models

class Poll(models.Model):
    question = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

class Choice(models.Model):
    poll = models.ForeignKey(Poll)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

 每个模块包含很多类，每个类就代表了一个数据库里面的表。

poll这个类包含了问题和创建问题的时间，choice这个类包含了选项描述和票数，ForeignKey这个函数告诉Choice都关联单一一个Poll。其实也就是数据库之间的关系。

激活我们的app

在mysite/settings.py这个文件中，修改如下：

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

 把polls这个app加到我们的项目中。（注意，以后如果文件在这个项目中只有唯一一个，不给出路径了，比如settings.py这个文件，在这次学习的教程中，只有mysite目录下才会有）

配置我们的数据库吧：python manage.py syncdb

都是英文，但是能看懂吧，密码是要输入的哈。

看看我们的数据库（使用的是默认的sqlite，网上下一个吧，要不然打不开这个文件奥）

注意下图的箭头

用shell来操作熟悉下数据库

python manage.py shell

C:Python27Libsite-packagesdjangoinmysite>python manage.py shell
Python 2.7.9 (default, Dec 10 2014, 12:24:55) [MSC v.1500 32 bit (Intel)] on win
32
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>>

 看看Poll这个类里面有什么数据

>>> from polls.models import Poll, Choice   # Import the model classes we just wrote.

# No polls are in the system yet.
>>> Poll.objects.all()
[]

# Create a new Poll.
# 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
>>> p = Poll(question="What's new?", pub_date=timezone.now())

# Save the object into the database. You have to call save() explicitly.
>>> p.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.
>>> p.id
1

# Access database columns via Python attributes.
>>> p.question
"What's new?"
>>> p.pub_date
datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>)

# Change values by changing the attributes, then calling save().
>>> p.question = "What's up?"
>>> p.save()

# objects.all() displays all the polls in the database.
>>> Poll.objects.all()
[<Poll: Poll object>]

 注释的英文就自己翻译下。

上面操作完成后，看看我们的数据库

成功加入了。

在使用Poll.objects.all()的时候输出的信息貌似没什么用，让我们改点东西

在models.py文件里面

class Poll(models.Model):
    question = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    def __unicode__(self):
        return self.question

class Choice(models.Model):
    poll = models.ForeignKey(Poll)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __unicode__(self):
        return self.choice_text

 在此运行，需要退出shell后(ctrl+z)，在进。

注意，unicode这个函数只能返回一个buffer或者string，tuple和list这种都不行奥。

在使用Poll.objects.all()的时候输出就对了。

让我们在poll里增加一个判断是否是最近发表的问题函数：

from django.db import models
import datetime
from django.utils import timezone

class Poll(models.Model):
    question = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    def __unicode__(self):
        return self.question

    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days = 1)

class Choice(models.Model):
    poll = models.ForeignKey(Poll)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __unicode__(self):
        return self.choice_text

 问题：如何修改数据库信息呢。提供一个方法，根据primarykey来获取对象进行修改

p = Poll.objects.get(pk=1)

p.question #打印

p.question = newstring #修改

p.save() #记得保存

 下面的代码一步一步操作吧，注释自己翻译了

>>> from polls.models import Poll, Choice

# Make sure our __unicode__() addition worked.
>>> Poll.objects.all()
[<Poll: What's up?>]

# Django provides a rich database lookup API that's entirely driven by
# keyword arguments.
>>> Poll.objects.filter(id=1)
[<Poll: What's up?>]
>>> Poll.objects.filter(question__startswith='What')
[<Poll: What's up?>]

# Get the poll that was published this year.
>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Poll.objects.get(pub_date__year=current_year)
<Poll: What's up?>

# Request an ID that doesn't exist, this will raise an exception.
>>> Poll.objects.get(id=2)
Traceback (most recent call last):
    ...
DoesNotExist: Poll 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 Poll.objects.get(id=1).
>>> Poll.objects.get(pk=1)
<Poll: What's up?>

# Make sure our custom method worked.
>>> p = Poll.objects.get(pk=1)
>>> p.was_published_recently()
True

# Give the Poll 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 poll's choices) which can be accessed via the API.
>>> p = Poll.objects.get(pk=1)

# Display any choices from the related object set -- none so far.
>>> p.choice_set.all()
[]

# Create three choices.
>>> p.choice_set.create(choice_text='Not much', votes=0)
<Choice: Not much>
>>> p.choice_set.create(choice_text='The sky', votes=0)
<Choice: The sky>
>>> c = p.choice_set.create(choice_text='Just hacking again', votes=0)

# Choice objects have API access to their related Poll objects.
>>> c.poll
<Poll: What's up?>

# And vice versa: Poll objects get access to Choice objects.
>>> p.choice_set.all()
[<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]
>>> p.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 poll whose pub_date is in this year
# (reusing the 'current_year' variable we created above).
>>> Choice.objects.filter(poll__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 = p.choice_set.filter(choice_text__startswith='Just hacking')
>>> c.delete()

 最后你的polls_choice表里面应该如下

总结：

其实内容不多，主要就是演示了创建项目，创建应用，以及使用的几个主要的命令和文件

主要命令 :

djang-admin.py startproject prjname

manage.py startapp appname

主要文件:

settings.py  用于配置，比如app，模版这些

models.py 主要是和数据库配置相关

数据库操作:

创建数据：就相当于创建一个类对象，最后要使用save函数进行保存

修改数据：使用primarykey获取对象后直接修改，save一下

obj = Ojbcet.objects.get(pk=1)
obj.sth = string
obj.save()

 数据筛选：主要使用filter，可以使用

关联数据库操作：需要在类名后面加上_set表明是一个数据集。

下一篇主要学习django强大的后台管理。