Django_初识（一）

学习笔记

一、创建一个服务器

需求：

1.熟悉操作命令
2.连接mysql数据库.
3.创建app=》polls
4.熟悉django的数据库操作命令

实践：

• 安装Django：
  1.我用的是Mac版pycharm，所以直接用内置安装第三方工具安装的Django

• 校验django是否安装成功

  $ python -c "import django; print(django.get_version())"
  

• 新建项目名：

  django-admin startproject mysite
  

  注：报错找不到django-admin解决方案：向/usr/local/bin/中添加软连接，也有可能是当前python路径没有执行权限sudo chmod +x django-admin.py

  软连接：

  sudo ln -s /usr/local/python27/python_path/django-admin.py /usr/local/bin/django-admin.py
  

• 设置TIME_ZONE:
  TIME_ZONE ='Asia/Shanghai'

• 使用Mysql数据库

  • 在mysite/settings.py中设置：

  
  DATABASES = {
      'default': {
          'ENGINE': 'django.db.backends.mysql',
          'NAME': 'db_wph',
          'USER': 'root',
          'PASSWORD': '123456',
          'HOST': '127.0.0.1',
          'PORT': '3306'
      }
  }
  

  • 然后使用命令：

    $ python manage.py migrate
    

• 测试一下服务器是否搭建成功：

  $ python manage.py runserver
  

  Performing system checks...
  
  0 errors found
  May 13, 2015 - 15:50:53
  Django version 1.8, using settings 'mysite.settings'
  Starting development server at http://127.0.0.1:8000/
  Quit the server with CONTROL-C.
  

  浏览器中输入网址：http://127.0.0.1:8000/

• 按control+c结束进程服务，并释放8000端口

  指定端口命令$ python manage.py runserver 8080

  监听所有端口：

  $ python manage.py runserver 0.0.0.0:8000
  

• 新建一个app=》polls

  $ python manage.py startapp polls
  

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

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

- 激活app,修改`mysite/settings.py`

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

• 运行命令：

  $ python manage.py makemigrations polls 
  

  通过运行makemigrations告诉Django，已经对模型做了一些更改（在这个例子中，你创建了一个新的模型）并且会将这些更改存储为迁移文件。

• 运行迁移命令：

  $ python manage.py sqlmigrate polls 0001
  

  • 再次运行migrate以在你的数据库中创建模型所对应的表：将这些改变更新到数据库中。

    $ python manage.py migrate
    

• 进入mysql查看表结构

  mysql> show tables;
  +----------------------------+
  | Tables_in_db_wph           |
  +----------------------------+
  | auth_group                 |
  | auth_group_permissions     |
  | auth_permission            |
  | auth_user                  |
  | auth_user_groups           |
  | auth_user_user_permissions |
  | city_list                  |
  | django_admin_log           |
  | django_content_type        |
  | django_migrations          |
  | django_session             |
  | polls_choice               |
  | polls_question             |
  | supplier                   |
  +----------------------------+
  14 rows in set (0.00 sec)
  

  ​

• 了解api命令 -操作数据库命令

  • 进入shell

  $ python manage.py shell
  

  >>> 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.
  >>> 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=)
  
  # 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()
  []
  

  ​

  mysql> select * from  polls_question;
  +----+---------------+----------------------------+
  | id | question_text | pub_date                   |
  +----+---------------+----------------------------+
  |  1 | what's up?    | 2016-10-20 06:58:26.437937 |
  +----+---------------+----------------------------+
  

  mysql> select * from  polls_choice;
  +----+--------------------+-------+-------------+
  | id | choice_text        | votes | question_id |
  +----+--------------------+-------+-------------+
  |  1 | Not much           |     0 |           1 |
  |  2 | The sky            |     0 |           1 |
  +----+--------------------+-------+-------------+
  3 rows in set (0.00 sec)
  

  >>> from polls.models import Question, Choice
  
  # Make sure our __str__() addition worked.
  >>> Question.objects.all()
  []
  
  # Django provides a rich database lookup API that's entirely driven by
  # keyword arguments.
  >>> Question.objects.filter(id=1)
  []
  >>> Question.objects.filter(question_text__startswith='What')
  []
  
  # 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)
  
  
  # 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)
  
  
  # 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()
  []
  
  # Create three choices.
  >>> q.choice_set.create(choice_text='Not much', votes=0)
  
  >>> q.choice_set.create(choice_text='The sky', votes=0)
  
  >>> c = q.choice_set.create(choice_text='Just hacking again', votes=0)
  
  # Choice objects have API access to their related Question objects.
  >>> c.question
  
  
  # And vice versa: Question objects get access to Choice objects.
  >>> q.choice_set.all()
  [, , ]
  >>> 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)
  [, , ]
  
  # Let's delete one of the choices. Use delete() for that.
  >>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
  >>> c.delete()
  

  ​