Django笔记

Posted 2020-09-18 天才源于勤奋 聪明在于积累

 

from app01 import models
models.Book.objects.create(name="python",price=88,pub_date=\'2017-05014\')

pymysql.err.IntegrityError: (1048, "Column \'publisher_id\' cannot be null")

 

models.Publisher.objects.create(name="TsingHua Publisher",website="http://www.tsinghuaedu.com")
<Publisher: Publisher object>
models.Publisher.objects.create(name="Youdian Publisher",website="http://www.youdianedu.com")

>>> models.Book.objects.create(name="python",price=88,pub_date=\'2017-05-14\',publisher_id=1)
<Book: Book object>

>>> models.Book.objects.create(name="linux",price=22,pub_date=\'2016-03-14\',publisher_id=1)
<Book: Book object>
>>> models.Book.objects.create(name="Go",price=50,pub_date=\'2018-09-14\',publisher_id=2)
<Book: Book object>

#查看所有的书籍
>>> models.Book.objects.all()
<QuerySet [<Book: Book object>, <Book: Book object>, <Book: Book object>]>

在modules下增加以下配置

def __str__(self):
return self.name

退出重新登录
D:\\python\\oldboy\\day16\\170514\\MyDjangoProject>python manage.py shell
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:18:55) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from app01 import models
>>> models.Book.objects.all()
<QuerySet [<Book: python>, <Book: linux>, <Book: Go>]>

字符串拼接:

def __str__(self):
return "%s %s"%(self.name,self.website)

>>> models.Book.objects.all()[0]
<Book: python>
>>> b1=models.Book.objects.all()[0]
>>> b1.authors
<django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager object at 0x000000000438F748>
>>> b1.authors.all() #查看作者
<QuerySet []>
>>> models.Author.objects.create(name=\'alex\',email=\'[e-mail]\')
<Author: Author object>
>>> models.Author.objects.create(name=\'jack\',email=\'[e-mail]\')
<Author: Author object>
>>> models.Author.objects.create(name=\'OldBoy\',email=\'[e-mail]\')
<Author: Author object>

创建作者
>>> b4=models.Book.objects.create(name="Jinpingmei",price=199,publisher_id=2,pub_date="2016-07-21")
>>> b4
<Book: Jinpingmei>
>>> b4.authors.add(1,2)
>>> b4.save()

删除作者
>>> b4.authors.remove(1)
>>> b4.save()

>>> b4.authors.all()
<QuerySet [<Author: jack>]>

 

查询
objects.filter 返回列表
objects.all 返回all
models.Book.objects.last() first()

>> p1.book_set.all() 多个图书关联了同一个出版社，通过出版社反向查出版了多少图书

objects.get 返回单个对象或错误
app01.models.DoesNotExist: Book matching query does not exist.
app01.models.MultipleObjectsReturned: get() returned more than one Book -- it re
objects.get_or_create() 如果没有就创建
>>> models.Book.objects.get_or_create(name="Java", publisher_id=2, pub_date="2019-01-02")
(<Book: Java>, True)

ORM之查（filter,value)

包含
>>> models.Book.objects.filter(name__contains="Go")
<QuerySet [<Book: Go>]>

---------------了不起的双下划线(__)之单表条件查询----------------

# models.Tb1.objects.filter(id__lt=10, id__gt=1) # 获取id大于1 且 小于10的值
#
# models.Tb1.objects.filter(id__in=[11, 22, 33]) # 获取id等于11、22、33的数据
# models.Tb1.objects.exclude(id__in=[11, 22, 33]) # not in
#
# models.Tb1.objects.filter(name__contains="ven")
# models.Tb1.objects.filter(name__icontains="ven") # icontains大小写不敏感
#
# models.Tb1.objects.filter(id__range=[1, 2]) # 范围bettwen and
#
# startswith，istartswith, endswith, iendswith,

查询相关API：

# <1>filter(**kwargs): 它包含了与所给筛选条件相匹配的对象

# <2>all(): 查询所有结果

# <3>get(**kwargs): 返回与所给筛选条件相匹配的对象，返回结果有且只有一个，如果符合筛选条件的对象超过一个或者没有都会抛出错误。

#-----------下面的方法都是对查询的结果再进行处理:比如 objects.filter.values()--------

# <4>values(*field): 返回一个ValueQuerySet——一个特殊的QuerySet，运行后得到的并不是一系列 model的实例化对象，而是一个可迭代的字典序列

# <5>exclude(**kwargs): 它包含了与所给筛选条件不匹配的对象

# <6>order_by(*field): 对查询结果排序

# <7>reverse(): 对查询结果反向排序

# <8>distinct(): 从返回结果中剔除重复纪录

# <9>values_list(*field): 它与values()非常相似，它返回的是一个元组序列，values返回的是一个字典序列

# <10>count(): 返回数据库中匹配查询(QuerySet)的对象数量。

# <11>first(): 返回第一条记录

# <12>last(): 返回最后一条记录

# <13>exists(): 如果QuerySet包含数据，就返回True，否则返回False

>>> models.Book.objects.filter(pub_date__range=(\'2015-01-01\',\'2017-01-01\'))
<QuerySet [<Book: linux>, <Book: Jinpingmei>]>
官方文档:
https://docs.djangoproject.com/en/1.11/ref/models/querysets/

__contains
__icontains 忽略大小写
__startswith
__endswith
__endswith
models.Book.objects.filter(pub_date__range=(\'2015-01-01\',\'2017-01-01\'))
Entry.objects.filter(pub_date__date=datetime.date(2005, 1, 1))

Entry.objects.filter(pub_date__year=2005)
Entry.objects.filter(pub_date__year__gte=2005)

Entry.objects.filter(pub_date__day=3)
Entry.objects.filter(pub_date__day__gte=3)

Entry.objects.filter(pub_date__week_day=2)
Entry.objects.filter(pub_date__week_day__gte=2)

Entry.objects.filter(pub_date__isnull=True)

>>> models.Book.objects.exclude(price=None) 反查询
<QuerySet [<Book: py>, <Book: linux>, <Book: Go>, <Book: Jinpingmei>]>

models.Book.objects.values(\'name\',\'price\')

aggregate 聚合

参考链接：https://docs.djangoproject.com/en/1.11/topics/db/aggregation/

from django.db.models import Avg,Max,Min,Sum,Count
>>> models.Book.objects.all().aggregate(Avg(\'price\'))

>>> models.Book.objects.values(\'publisher__name\').annotate(Avg(\'price\')) 统计所有书籍的平均价格
<QuerySet [{\'publisher__name\': \'TsingHua Publisher\', \'price__avg\': 22.0}, {\'publ
isher__name\': \'Youdian Publisher\', \'price__avg\': 124.5}]>
>>> models.Book.objects.all().aggregate(Avg(\'price\'))
{\'price__avg\': 89.75}
>>> models.Book.objects.values(\'name\',\'price\').count()
6

>>> models.Book.objects.create(name="py3 dev",publisher_id=1,pub_date=\'2018-09-10\')
<Book: py3 dev>

正则匹配
>>> models.Book.objects.filter(name__regex=r"^G")
<QuerySet [<Book: Go>]>
>>> models.Book.objects.filter(name__regex=r"o$")
<QuerySet [<Book: Go>]>

Entry.objects.get(title__regex=r\'^(An?|The) +\')

 

>>> from django.db.models import Avg,Sum,Count
>>> models.Book.objects.values(\'publisher__name\').annotate(Count(\'id\'))
<QuerySet [{\'publisher__name\': \'TsingHua Publisher\', \'id__count\': 3}, {\'publishe
r__name\': \'Youdian Publisher\', \'id__count\': 3}]>

>>> models.Book.objects.values(\'publisher__name\').annotate(Avg(\'price\'))
<QuerySet [{\'price__avg\': 55.0, \'publisher__name\': \'TsingHua Publisher\'}, {\'pric
e__avg\': 124.5, \'publisher__name\': \'Youdian Publisher\'}]>

 

F：将所有书籍价格取出来分别+10

>>> from django.db.models import F
>>> models.Book.objects.values(\'price\')
<QuerySet [{\'price\': 88}, {\'price\': 22}, {\'price\': 50}, {\'price\': 199}, {\'price\'
: None}, {\'price\': None}]>
>>> models.Book.objects.update(price=F(\'price\')+10)
6
>>> models.Book.objects.values(\'price\')
<QuerySet [{\'price\': 98}, {\'price\': 32}, {\'price\': 60}, {\'price\': 209}, {\'price\'
: None}, {\'price\': None}]>

http://www.cnblogs.com/alex3714/articles/5512568.html

F
自修改
Entry.objects.all().update(n_pingbacks=F(\'n_pingbacks\') + 1)
本表内两个字段比较
>>> from django.db.models import F
>>> Entry.objects.filter(n_comments__gt=F(\'n_pingbacks\'))
字段数据迁移
# THIS WILL RAISE A FieldError
>>> Entry.objects.update(headline=F(\'blog__name\'))
Q