python中的细节

# 1
# li = ['a', 'b', 'c', 'd','e']
# print(li[10:])    #[] 不报错

# 2
# 这不是True或False，而是值
# 另外，优先级 not > and > or
# print(1 and 2 or 3)    # 2
# print(2 and 0 or 1)    # 1
# print(1 or 2 and 0)    # 1
# print(2 or 0 and 1)    # 2
# print(not 1 and 0)

# 3
# x1 = 'a'
# x2 = 'b'
# list1 = [1,2]
# list2 = [3,4]
# list3 = [5,6]
# list4 = [x1, x2, list1, list2, list3]    # ['a', 'b', [1,2], [3,4], [5,6]]
#
# ### 考察对"引用"的理解
#
# x1 = 'c'                                # x1 = 'c'
# list1[0] = 7                            # list1 = [7,2]
# print(list4)                            # ['a', 'b', [7,2], [3,4], [5,6]]
#
# list4[1] = 'd'                          # ['a', 'd', [7,2], [3,4], [5,6]]
# print(x2)                               # 'b'
#
# list4[3] = [8,9]                        # ['a', 'd', [7,2], [8,9], [5,6]]
# print(list2)                            # [3,4]，
#                                         # 也就是修改list4的引用，原来指向list2，现在指向[8,9]，所以对list2没影响。
#
# list4[4][1] = 10                        # ['a', 'd', [7,2], [8,9], [5,10]]
# print(list3)                            # [5,6]，
#                                         # 这个做错了，list4[4]还是指向list3，修改list4[4][1]已经影响到了list3。
# print(list4)

# 4
# 下面是否有错：
# def calc(a, b, c, d=1, e=2):
#     return (a + b) * (c - d) + e
#
# print(calc(1, 2, 3, d=5, 4))    #关键字参数一定要放到位置参数后面

# 5
# 互换
# x = [0,1]
# i = 0
# i,x[i] = 1,2
# print(x)    # [0,2]

# a = 1
# b = 2
# a, b = b, a
# print(a,b)

Django：

MVC：model、view、controller

MTV：model、template、view

django-admin startproject mysite

python manage.py startapp myapp (mysite目录下执行)

python manage.py runserver 8080 (默认8000)

添加模板：

根目录下创建文件夹templates(名字任意，只是需要与settings.py中对应)

settings.py中设置'DIRS': [os.path.join(BASE_DIR, 'templates')],

给html文件传参：

 def retok(req):
     date = datetime.datetime.now()
     return render(req, 'ret.html', {'date': date})  # django没有'**'

post方法403 Forbidden：

中间件，'django.middleware.csrf.CsrfViewMiddleware',

请求方法大写：

 def info(req):
     if req.method == 'POST':  # 必须大写
         print(req.POST.get('name'))  # 接收请求信息
         return HttpResponse('ok')
     return render(req, 'info.html')

模板jinjia2取值：

无论列表还是字典都可用 '.'

 {{info_list.0}}
 <table border="1">
     {% for info in info_list %}
         <td>{{ info.name }}</td>
         <td>{{ info.age }}</td>
 {% endfor %}
 </table>

model模块：

创建model之后，初始化之前需要在settings.py中配置app，

 INSTALLED_APPS = [
     ...
     'myapp'
 ]

python manage.py makemigrations

python manage.py migrate

一个pycharm社区版引起的血案：

执行数据库初始化之后，怎么也找不到database插件，原因是pycharm社区版只支持纯python开发，专业版才支持HTML、JS、SQL。

sqlite3表中插入数据：

 # model.py

 class Info(models.Model):
     name = models.CharField(max_length=10)
     age = models.CharField(max_length=10)
     pwd = models.CharField(max_length=10) 

 # views.py

     Info.objects.create(
         name=n,
         age=a,
         pwd=p,
     )

配置静态文件，以jQuery为例：

 # settings.py

 STATIC_URL = '/yangxl/'  # html中寻找静态文件用的是该路径

 STATICFILES_DIRS = [
     (os.path.join(BASE_DIR, 'static')),  # 文件名任意, 但逗号不能丢
 ]

 # .html

 <h1>旺财</h1>
 <script src="/yangxl/jquery-3.4.1.min.js"></script>
 <script>
     $('h1').css('color', 'red')
 </script>

路由匹配：path、re_path，

通过正则分组给视图函数传参

 # urls.py

 from django.urls import path, re_path
 from myapp import views

 urlpatterns = [
     path('admin/', admin.site.urls),
     re_path(r'info/([0-9]{3})', views.info),
 ]

 # views.py

 def info(req, n):
     return HttpResponse(n)

关键字参数，

 # urls.py

     re_path(r'info/(?P<num1>[0-9]{3})/(?P<num2>[0-9])', views.info),

 # views.py

 def info(req, num1, num2):
     return HttpResponse(num1+num2)  # 字符串拼接

传入一个与路径无关的参数，

     re_path(r'info/(?P<num1>[0-9]{3})/(?P<num2>[0-9])', views.info, {'environ': 'yangxl'}),

别名name，当访问url发生变化时，不需修改form、a等二次访问的url，

 # urls.py

     re_path(r'info', views.info, name='genesis'),

 # .html

 <form action="{% url 'genesis' %}" method="post">
     <input type="text" name="user">
     <input type="password" name="pwd">
     <input type="submit" value="提交">
 </form>

include，路由分发，

 # urls.py

 from django.urls import path, include

 urlpatterns = [
     ...
     path('backend', include('backend.urls')),
 ]

 # app.urls.py

 from django.urls import path, re_path
 from backend import views

 urlpatterns = [
     re_path('info', views.info, name='genesis'),
 ]

 访问：http://127.0.0.1:8080/backend/info

req为WSGIRequest对象，

from django.core.handlers.wsgi import WSGIRequest
from django.http import HttpRequest

返回一个HttpResponse对象，

from django.http import HttpResponse
render、render_to_response、redirect、HttpResponse

django命令行模式：

 python manage.py shell

 In [1]: from django.template import Template, Context

 In [2]: t = Template('hello{{name}}')

 In [3]: c = Context({'name': 'wangcai'})

 In [4]: t.render(c)
 Out[4]: 'hellowangcai'

关于import，无论是在mysite.urls.py还是backend.urls.py都能导入views (from backend import views)，因为环境变量sys.path[0]为项目根目录。

模板语法提示功能：

Settings -- Editor -- Inspections -- Django、python都选上。

forloop.counter、forloop.counter0：

 {% for i in l%}
     <p>{{ forloop.counter0 }}: {{ i }}</p>
 {% endfor %}

filter：'|'

 {{ s }}
 {{ s|upper }}
 {{ s|capfirst }}

autoescape：

效果等同于{{ s|safe }}

 def info(req):
     s = '<a href="#">中南海</a>'
     return render(req, 'index.html', {'s': s})

 {% autoescape off %}  # 结果渲染，意会!!
     {{ s }}
 {% endautoescape %}

{% csrf_token %}：

解决post方法遇到的403 Forbidden问题，

 # .html
 <form action="info" method="post">
     <input type="text" name="user">
     <input type="pwd" name="pwd">
     <input type="submit" value="submit">
     {% csrf_token %}
 </form>

 提交表单时多加一个input标签，
 <input name="csrfmiddlewaretoken" type="hidden" value="5i5jCtZj8PRpxha7U6Tct2lxEvXyTUQ0iIaswDqRhXNI2SGXjNoWyMYiMDlNm3B4">

不渲染，{{ s }}

 {% verbatim %}
     {{ s }}
 {% endverbatim %}

 结果：{{ s }} 

自定制模板函数：

必须在已注册app中创建名为templatetags的文件夹，文件夹下的文件名任意，(已注册是指在settings.INSTALLED_APPS中)。

 # views.py

 def info(req):
     s = 'wangcai'
     return render(req, 'index.html', {'s': s})

 # templatetags.customs.py

 from django import template

 register = template.Library()  # register

 @register.simple_tag  # simple_tag
 def use_salt(s):
     return 'hello, ' + s

 # .html

 {% load customs %}  # 在使用之前导入模块

 {% use_salt s %}  # 去导入的模块customs.py中获取函数并执行

自定制过滤器：只有装饰器和调用方式不同，

 # customs.py

 @register.filter
 def ...

 # .html

 {{ s|use_salt }}

二者加参数，

 {% use_salt s 'come here' %}
 {{ s|use_salt:', come here' }}

extends：在母版中定义共同的部分和一个盒子，在子模版中导入母版并用各自的内容填充盒子

 # base.html

 <!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>Title</title>
     <style>
         .page-header{
             height: 50px;
             background-color: rebeccapurple;
         }
         .page-body .menu{
             height: 500px;
             background-color: antiquewhite;
             float: left;
             width: 20%;
         }
         .page-body .content{
             height: 500px;
             background-color: cornflowerblue;
             float: left;
             width: 80%;
         }
         .page-footer{
             height: 50px;
             background-color: darkcyan;
             clear: both;
         }
     </style>
 </head>
 <body>
 <div>
     <div class="page-header"></div>
     <div class="page-body">
         <div class="menu">
             <a href="/order">订单</a>
             <a href="/shop">购物</a>
         </div>
         {% block aigo %}  # 盒子

         {% endblock %}
     </div>
     <div class="page-footer"></div>
 </div>
 </body>
 </html>

 # order.html

 {% extends 'base.html' %}  # 导入母版

 {% block aigo %}  # 填充盒子
     <div class="content">
         订单啊
     </div>
 {% endblock %}

model、ORM：

单表操作：

     # 增
     user = {'name': 'grute', 'age': 3, 'pwd': 123}
     models.Info.objects.create(**user)

     # 查
     users = models.Info.objects.all()
     users = models.Info.objects.filter(id__gte=1)  # <QuerySet []>, 双下划线, 可切片操作
     users = models.Info.objects.get(id=1)  # 找不到数据会报错
     users = models.Info.objects.all().values('id', 'name')  # 特定字段
     users = models.Info.objects.exclude(id=3)  # 反向查找
     users = models.Info.objects.exclude(id=3).count()  # 计数
     users = models.Info.objects.filter(id=2).last()
     users = models.Info.objects.filter(id=2).first()
     users = models.Info.objects.filter(id=1).exists()  # 是否存在该条数据, bool, 惰性机制(比如, 还有迭代器)
     print('uu', users)

     # 改
     models.Info.objects.filter(id=2).update(name='wangcai', age=16)  # update是QuerySet的方法

     # 删
     models.Info.objects.filter(id=1).delete()

     # 排序
     users = models.Info.objects.order_by('-id')  # 倒序
     print('uu', users)

联表操作：一对一、多对一、多对多

 # models.py

 class Book(models.Model):
     title = models.CharField(max_length=64)
     price = models.IntegerField()
     color = models.CharField(max_length=64)
     page_num = models.IntegerField(null=True)
     publisher = models.ForeignKey('Publisher', models.CASCADE)
     # 接受对象
     author = models.ManyToManyField('Author')  # 多对多, 放到Author中也可

     def __str__(self):
         return self.title

 class Publisher(models.Model):
     name = models.CharField(max_length=64)
     city = models.CharField(max_length=63)

     def __str__(self):
         return self.name

 class Author(models.Model):
     name = models.CharField(max_length=30)

     def __str__(self):
         return self.name

 # views.py

 def info(req):
     # models.Publisher.objects.create(
     #     name='新东方技工学校',
     #     city='济南',
     # )

     # models.Author.objects.create(
     #     name='紫英'
     # )

     # pubs = models.Publisher.objects.filter(city='济南')
     # author1 = models.Author.objects.get(id=2)
     # author2 = models.Author.objects.get(id=3)
     # print('aa', author2)

     # book = models.Book.objects.create(
     #     title='挖掘机切磋技法',
     #     price=32,
     #     color='blue3',
     #     # 多对一,  二选一
     #     # publisher_id=2,  # id
     #     publisher=pubs[0]  # 对象, 推荐
     # )
     # 多对多
     # 正向查询
     # book = models.Book.objects.filter(id=3)[0]
     # authors = models.Author.objects.filter(id=3)
     # book.author.remove(*authors)  # 类似集合操作，删除为remove
     # 反向查询
     author = models.Author.objects.filter(id=3)[0]
     books = models.Book.objects.filter(id__gte=2)
     author.book_set.add(*books)

     return HttpResponse('ok')

多对一查找：

     # 多对一
     # 正查
     book = models.Book.objects.filter(title='挖掘机切磋技法')[0]
     print(book.publisher.name)
     # 反查
     pubs = models.Publisher.objects.filter(name='新东方技工学校')[0]
     print(pubs.book_set.values('title'))  # QuerySet
     print(pubs.book_set.values('title').distinct())  # 根据title去重

手动创建第三张表，这样就不需创建多对多字段了

 # models.py

 class Book2Author(models.Model):
     book = models.ForeignKey('Book', models.CASCADE)
     author = models.ForeignKey('Author', models.CASCADE)

     class Meta:
         unique_together = ['book', 'author']

 # views.py
     # 直接插入数据
     author = models.Author.objects.filter(id=3)[0]
     book = models.Book.objects.filter(id__gte=2)[0]
     models.Book2Author.objects.create(
         book=book,
         author=author
     )

一对一：

 # models.py

     # publisher = models.ForeignKey('Publisher', models.CASCADE, unique=True)
     publisher = models.OneToOneField('Publisher', on_delete=models.CASCADE)  # 推荐

双下划线，条件查询：

     # 单表查询
     # book = models.Book.objects.filter(id__range=[4, 7])
     # book = models.Book.objects.filter(id__in=[3, 5])
     # book = models.Book.objects.filter(title__contains='技法')
     # book = models.Book.objects.filter(title__icontains='技法')  # 不区分大小写
     # book = models.Book.objects.filter(title__startswith='酸菜')

     # 正向多对一
     # books = models.Book.objects.filter(title='挖掘机切磋技法').values('id')
     # books = models.Book.objects.filter(title='挖掘机切磋技法').values('publisher__city')

     # 正向多对多
     # books = models.Book.objects.filter(author__name='菱纱').values('title')

     # 反向一对多
     # pubs = models.Publisher.objects.filter(book__title='挖掘机切磋技法').values('name')
     # pubs = models.Publisher.objects.filter(book__title='酸菜鱼攻略').values('book__author__name')

     # 反向多对多
     authr = models.Author.objects.filter(book__title='挖掘机切磋技法').values('name')
     print(authr)

django日志配置，

可用于验证filter等的惰性机制(只有使用filter的返回结果时真正执行sql语句)

 LOGGING = {
     'version': 1,
     'disable_existing_loggers': False,
     'handlers': {
         'console': {
             'level': 'DEBUG',
             'class': 'logging.StreamHandler',
         },
     },
     'loggers': {
         'django.db.backends': {
             'handlers': ['console'],
             'propagate': True,
             'level': 'DEBUG',
         },
     }
 }

缓存机制：

     pubs = models.Publisher.objects.filter(city='成都')
     for p in pubs:
         print(p)

     # pubs.update(city='重庆')

     for p in pubs:  # 当再次执行遍历操作且遍历数据未改变时, 数据是从缓存中获取的, 不会重复执行sql查询
         print(p)

以下两条不会把数据加载到缓存，

     pubs = models.Publisher.objects.filter(city='重庆').exists()
     pubs = models.Publisher.objects.filter(city='成都').iterator()

聚合查询、分组查询，

aggregate和annotate：

     from django.db.models import Avg, Min, Max, Sum

     # 查询菱纱出的书的均价
     # books = models.Book.objects.filter(author__name='菱纱').aggregate(Avg('price'))  # 聚合查询

     # 查询各个作者出的书的总价格
     # books = models.Book.objects.values('author__name')
     # books = models.Book.objects.values('author__name').annotate(Sum('price'))  # annotate对作者分组(可重复), 然后按价格聚合

     # 查询各个出版社最便宜的书的价格
     # books = models.Book.objects.values('publisher').annotate(Min('price'))

F和Q查询：

     from django.db.models import F, Q

     # 把菱纱出的书的价格提高100
     books = models.Book.objects.filter(author__name='菱纱').update(price=F('price')+100)  # 返回更新数据的个数

     # &、|、～
     books = models.Book.objects.filter(Q(id=3) | Q(price__lt=100))  # 或关系
     books = models.Book.objects.filter(Q(id__gte=5) & Q(price__lt=150), color='green')  # 关键字参数放在Q后面
     

Admin:

python manage.py createsuperuser

汉化：

 # LANGUAGE_CODE = 'en-us'
 LANGUAGE_CODE = 'zh-Hans'

指定表字段，verbose_name，后加的不需数据库初始化

 title = models.CharField(max_length=64, verbose_name='书名')

设置某字段只读，editable

 title = models.CharField(max_length=64, verbose_name='书名', editable=False)

django连接mysql：

 ImproperlyConfigured: mysqlclient 1.3.13 or newer is required; you have
 0.9.3.
 # django.db.backends.mysql.base.py

 py3中编码也有问题
 # django.db.backends.mysql.operations.py

 # settings.py

 DATABASES = {
     'default': {
         # 'ENGINE': 'django.db.backends.sqlite3',
         # 'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),

         'ENGINE': 'django.db.backends.mysql',
         'HOST': '127.0.0.1',
         'PORT': '',
         'USER': 'root',
         'PASSWORD': '',
         'NAME': 'wangcai',
     }
 }

 # app下的__init__.py

 import pymysql
 pymysql.install_as_MySQLdb()

 # 初始化
 python manage.py makemigrations
 python manage.py migrate

 # django-database插件显示mysql，这个因为时区问题无法连接，懒得配置了。。

django-database插件显示mysql，这个因为时区不匹配而无法连接，需要做以下配置，

 # 修改mysql时区为东八区

 show variables like '%time_zone%';
 set global time_zone='+8:00';
 flush privileges;

非常秀的博客：

https://www.cnblogs.com/yuanchenqi/articles/6083427.html