Django框架学习(一)

项目创建步骤

• $ django-admin startproject mysite 创建一个名为mysite的项目
• $ python manage.py startapp polls 在manage.py目录下创建polls模块
• 在polls模块中添加urls.py,最终在mysite模块中include该模块即可

# polls/urls.py
from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

# mysite/urls.py
from django.contrib import admin
from django.urls import include, path

urlpatterns = [
  	# 引入polls模块中的url 
    path('polls/', include('polls.urls')),
    path('admin/', admin.site.urls),
]

• 数据库配置我这里选用了mysql，有坑的地方看下文详细介绍

• $ python manage.py migrate创建框架自带应用

  • django.contrib.admin – 管理员站点， 你很快就会使用它。
  • django.contrib.auth – 认证授权系统。
  • django.contrib.contenttypes – 内容类型框架。
  • django.contrib.sessions – 会话框架。
  • django.contrib.messages – 消息框架。
  • django.contrib.staticfiles – 管理静态文件的框架。

• 创建model去自动生成表

from django.db import models

class Question(models.Model):
   # question_text字段名称,CharField字符串类型,max_length最大长度
    question_text = models.CharField(max_length=200)
    # DateTimeField日期类型的字段datetime
    pub_date = models.DateTimeField('date published')

class Choice(models.Model):
  	# 设置外键，对象为Question类
    # 这里有个问题 明明设置的删除时方法是CASCADE但实际上数据库查看是RESTRICT，经验证模式并没有生效
    #   CONSTRAINT `polls_choice_question_id_c5b4b260_fk_polls_question_id` FOREIGN KEY (`question_id`) REFERENCES `polls_question` (`id`) ON DELETE CASCADE （CASCADE时DDL）
		#   CONSTRAINT `polls_choice_question_id_c5b4b260_fk_polls_question_id` FOREIGN KEY (`question_id`) REFERENCES `polls_question` (`id`)  (RESTRICT时DDL)
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

• 激活模型，自动为这个模型创建数据库schema
  • 在settings.py配置文件中找到INSTALLED_APPS配置类并添加polls.apps.PollsConfig
  • 执行python manage.py makemigrations pollsDjango 会检测你对模型文件的修改，生成0001_initial.py
  • 执行python manage.py migrate创建数据库表

坑

1. 查阅官方文档安装python的mysql驱动，官方推荐为mysqlclientpip install mysqlclient报错为OSError: mysql_config not found,查阅github，发现人家已经给了你提示

macOS (Homebrew)
Install MySQL and mysqlclient:

# Assume you are activating Python 3 venv
$ brew install mysql
$ pip install mysqlclient
If you don't want to install MySQL server, you can use mysql-client instead:

# Assume you are activating Python 3 venv
$ brew install mysql-client
$ echo 'export PATH="/usr/local/opt/mysql-client/bin:$PATH"' >> ~/.bash_profile
$ export PATH="/usr/local/opt/mysql-client/bin:$PATH"
$ pip install mysqlclient