python 自定義模塊，python staticsmodels用法_python自動化之models 進階操作二

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python 自定義模塊？# PUBLIC METHODS THAT ALTER ATTRIBUTES AND RETURN A NEW QUERYSET #

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python爬蟲教程，def all(self)

# 獲取所有的數據對象

def filter(self, *args, **kwargs)

# 條件查詢

# 條件可以是：參數，字典，Q

def exclude(self, *args, **kwargs)

# 條件查詢

# 條件可以是：參數，字典，Q

def select_related(self, *fields)

性能相關：表之間進行join連表操作，一次性獲取關聯的數據。

model.tb.objects.all().select_related()

model.tb.objects.all().select_related('外鍵字段')

model.tb.objects.all().select_related('外鍵字段__外鍵字段')

def prefetch_related(self, *lookups)

性能相關：多表連表操作時速度會慢，使用其執行多次SQL查詢在Python代碼中實現連表操作。

# 獲取所有用戶表

# 獲取用戶類型表where id in (用戶表中的查到的所有用戶ID)

models.UserInfo.objects.prefetch_related('外鍵字段')

from django.db.models import Count, Case, When, IntegerField

Article.objects.annotate(

numviews=Count(Case(

When(readership__what_time__lt=treshold, then=1),

output_field=CharField(),

))

)

students = Student.objects.all().annotate(num_excused_absences=models.Sum(

models.Case(

models.When(absence__type='Excused', then=1),

default=0,

output_field=models.IntegerField()

)))

def annotate(self, *args, **kwargs)

# 用于實現聚合group by查詢

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

v = models.UserInfo.objects.values('u_id').annotate(uid=Count('u_id'))

# SELECT u_id, COUNT(ui) AS `uid` FROM UserInfo GROUP BY u_id

v = models.UserInfo.objects.values('u_id').annotate(uid=Count('u_id')).filter(uid__gt=1)

# SELECT u_id, COUNT(ui_id) AS `uid` FROM UserInfo GROUP BY u_id having count(u_id) > 1

v = models.UserInfo.objects.values('u_id').annotate(uid=Count('u_id',distinct=True)).filter(uid__gt=1)

# SELECT u_id, COUNT( DISTINCT ui_id) AS `uid` FROM UserInfo GROUP BY u_id having count(u_id) > 1

def distinct(self, *field_names)

# 用于distinct去重

models.UserInfo.objects.values('nid').distinct()

# select distinct nid from userinfo

注：只有在PostgreSQL中才能使用distinct進行去重

def order_by(self, *field_names)

# 用于排序

models.UserInfo.objects.all().order_by('-id','age')

def extra(self, select=None, where=None, params=None, tables=None, order_by=None, select_params=None)

# 構造額外的查詢條件或者映射，如：子查詢

Entry.objects.extra(select={'new_id': "select col from sometable where othercol > %s"}, select_params=(1,))

Entry.objects.extra(where=['headline=%s'], params=['Lennon'])

Entry.objects.extra(where=["foo='a' OR bar = 'a'", "baz = 'a'"])

Entry.objects.extra(select={'new_id': "select id from tb where id > %s"}, select_params=(1,), order_by=['-nid'])

def reverse(self):

# 倒序

models.UserInfo.objects.all().order_by('-nid').reverse()

# 注：如果存在order_by，reverse則是倒序，如果多個排序則一一倒序

def defer(self, *fields):

models.UserInfo.objects.defer('username','id')

或

models.UserInfo.objects.filter(...).defer('username','id')

#映射中排除某列數據

def only(self, *fields):

#僅取某個表中的數據

models.UserInfo.objects.only('username','id')

或

models.UserInfo.objects.filter(...).only('username','id')

def using(self, alias):

指定使用的數據庫，參數為別名(setting中的設置)

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# PUBLIC METHODS THAT RETURN A QUERYSET SUBCLASS #

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def raw(self, raw_query, params=None, translations=None, using=None):

# 執行原生SQL

models.UserInfo.objects.raw('select * from userinfo')

# 如果SQL是其他表時，必須將名字設置為當前UserInfo對象的主鍵列名

models.UserInfo.objects.raw('select id as nid from 其他表')

# 為原生SQL設置參數

models.UserInfo.objects.raw('select id as nid from userinfo where nid>%s', params=[12,])

# 將獲取的到列名轉換為指定列名

name_map = {'first': 'first_name', 'last': 'last_name', 'bd': 'birth_date', 'pk': 'id'}

Person.objects.raw('SELECT * FROM some_other_table', translations=name_map)

# 指定數據庫

models.UserInfo.objects.raw('select * from userinfo', using="default")

################### 原生SQL ###################

from django.db import connection, connections

cursor = connection.cursor() # cursor = connections['default'].cursor()

cursor.execute("""SELECT * from auth_user where id = %s""", [1])

row = cursor.fetchone() # fetchall()/fetchmany(..)

def values(self, *fields):

# 獲取每行數據為字典格式

def values_list(self, *fields, **kwargs):

# 獲取每行數據為元祖

def dates(self, field_name, kind, order='ASC'):

# 根據時間進行某一部分進行去重查找并截取指定內容

# kind只能是："year"(年), "month"(年-月), "day"(年-月-日)

# order只能是："ASC" "DESC"

# 并獲取轉換后的時間

- year : 年-01-01

- month: 年-月-01

- day : 年-月-日

models.DatePlus.objects.dates('ctime','day','DESC')

def datetimes(self, field_name, kind, order='ASC', tzinfo=None):

# 根據時間進行某一部分進行去重查找并截取指定內容，將時間轉換為指定時區時間

# kind只能是 "year", "month", "day", "hour", "minute", "second"

# order只能是："ASC" "DESC"

# tzinfo時區對象

models.DDD.objects.datetimes('ctime','hour',tzinfo=pytz.UTC)

models.DDD.objects.datetimes('ctime','hour',tzinfo=pytz.timezone('Asia/Shanghai'))

"""

pip3 install pytz

import pytz

pytz.all_timezones

pytz.timezone(‘Asia/Shanghai’)

"""

def none(self):

# 空QuerySet對象

####################################

# METHODS THAT DO DATABASE QUERIES #

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def aggregate(self, *args, **kwargs):

# 聚合函數，獲取字典類型聚合結果

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

result = models.UserInfo.objects.aggregate(k=Count('u_id', distinct=True), n=Count('nid'))

===> {'k': 3, 'n': 4}

def count(self):

# 獲取個數

def get(self, *args, **kwargs):

# 獲取單個對象

def create(self, **kwargs):

# 創建對象

def bulk_create(self, objs, batch_size=None):

# 批量插入

# batch_size表示一次插入的個數

objs = [

models.DDD(name='r11'),

models.DDD(name='r22')

]

models.DDD.objects.bulk_create(objs, 10)

def get_or_create(self, defaults=None, **kwargs):

# 如果存在，則獲取，否則，創建

# defaults 指定創建時，其他字段的值

obj, created = models.UserInfo.objects.get_or_create(username='root1', defaults={'email': '1111111','u_id': 2, 't_id': 2})

def update_or_create(self, defaults=None, **kwargs):

# 如果存在，則更新，否則，創建

# defaults 指定創建時或更新時的其他字段

obj, created = models.UserInfo.objects.update_or_create(username='root1', defaults={'email': '1111111','u_id': 2, 't_id': 1})

def first(self):

# 獲取第一個

def last(self):

# 獲取最后一個

def in_bulk(self, id_list=None):

# 根據主鍵ID進行查找

id_list = [11,21,31]

models.DDD.objects.in_bulk(id_list)

def delete(self):

# 刪除

def update(self, **kwargs):

# 更新

def exists(self):

# 是否有結果

其他操作