flask之SQLAlchemy

時間  2019-11-13
標籤 flask sqlalchemy 欄目 Python 简体版
原文   原文鏈接

本篇導航：

 

一. 介紹html

SQLAlchemy是一個基於Python實現的ORM框架。該框架創建在 DB API之上，使用關係對象映射進行數據庫操做，簡言之即是：將類和對象轉換成SQL，而後使用數據API執行SQL並獲取執行結果。python

pip install sqlalchemy -i http://pypi.douban.com/simple  --trusted-host pypi.douban.com

組成部分：mysql

  • Engine，框架的引擎
  • Connection Pooling ，數據庫鏈接池
  • Dialect，選擇鏈接數據庫的DB API種類
  • Schema/Types，架構和類型
  • SQL Exprression Language，SQL表達式語言

SQLAlchemy自己沒法操做數據庫，其必須以來pymsql等第三方插件，Dialect用於和數據API進行交流，根據配置文件的不一樣調用不一樣的數據庫API，從而實現對數據庫的操做，如：sql

MySQL-Python
    mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>
    
pymysql
    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
    
MySQL-Connector
    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>
    
cx_Oracle
    oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]
    
更多：http://docs.sqlalchemy.org/en/latest/dialects/index.html
View Code

 

二. 使用數據庫

一、 執行原生SQL語句flask

import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine
 
engine = create_engine(
    "mysql+pymysql://root:123@127.0.0.1:3306/t1?charset=utf8",
    max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
    pool_size=5,  # 鏈接池大小
    pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
    pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
)
 
 
def task(arg):
    conn = engine.raw_connection()
    cursor = conn.cursor()
    cursor.execute(
        "select * from t1"
    )
    result = cursor.fetchall()
    cursor.close()
    conn.close()
 
 
for i in range(20):
    t = threading.Thread(target=task, args=(i,))
    t.start()
View Code 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5)


def task(arg):
    conn = engine.contextual_connect()
    with conn:
        cur = conn.execute(
            "select * from t1"
        )
        result = cur.fetchall()
        print(result)


for i in range(20):
    t = threading.Thread(target=task, args=(i,))
    t.start()
View Code 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine
from sqlalchemy.engine.result import ResultProxy
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5)


def task(arg):
    cur = engine.execute("select * from t1")
    result = cur.fetchall()
    cur.close()
    print(result)


for i in range(20):
    t = threading.Thread(target=task, args=(i,))
    t.start()
View Code

注意: 查看鏈接 show status like 'Threads%';安全

2.、ORMsession

a.、建立數據庫表多線程

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index

Base = declarative_base()


class Users(Base):
    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)
    name = Column(String(32), index=True, nullable=False)
    # email = Column(String(32), unique=True)
    # ctime = Column(DateTime, default=datetime.datetime.now)
    # extra = Column(Text, nullable=True)

    __table_args__ = (
        # UniqueConstraint('id', 'name', name='uix_id_name'),
        # Index('ix_id_name', 'name', 'email'),
    )


def init_db():
    """
    根據類建立數據庫表
    :return: 
    """
    engine = create_engine(
        "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
    )

    Base.metadata.create_all(engine)


def drop_db():
    """
    根據類刪除數據庫表
    :return: 
    """
    engine = create_engine(
        "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
    )

    Base.metadata.drop_all(engine)


if __name__ == '__main__':
    drop_db()
    init_db()
建立單表 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from sqlalchemy.orm import relationship

Base = declarative_base()


# ##################### 單表示例 #########################
class Users(Base):
    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)
    name = Column(String(32), index=True)
    age = Column(Integer, default=18)
    email = Column(String(32), unique=True)
    ctime = Column(DateTime, default=datetime.datetime.now)
    extra = Column(Text, nullable=True)

    __table_args__ = (
        # UniqueConstraint('id', 'name', name='uix_id_name'),
        # Index('ix_id_name', 'name', 'extra'),
    )


class Hosts(Base):
    __tablename__ = 'hosts'

    id = Column(Integer, primary_key=True)
    name = Column(String(32), index=True)
    ctime = Column(DateTime, default=datetime.datetime.now)


# ##################### 一對多示例 #########################
class Hobby(Base):
    __tablename__ = 'hobby'
    id = Column(Integer, primary_key=True)
    caption = Column(String(50), default='籃球')


class Person(Base):
    __tablename__ = 'person'
    nid = Column(Integer, primary_key=True)
    name = Column(String(32), index=True, nullable=True)
    hobby_id = Column(Integer, ForeignKey("hobby.id"))

    # 與生成表結構無關，僅用於查詢方便
    hobby = relationship("Hobby", backref='pers')


# ##################### 多對多示例 #########################

class Server2Group(Base):
    __tablename__ = 'server2group'
    id = Column(Integer, primary_key=True, autoincrement=True)
    server_id = Column(Integer, ForeignKey('server.id'))
    group_id = Column(Integer, ForeignKey('group.id'))


class Group(Base):
    __tablename__ = 'group'
    id = Column(Integer, primary_key=True)
    name = Column(String(64), unique=True, nullable=False)

    # 與生成表結構無關，僅用於查詢方便
    servers = relationship('Server', secondary='server2group', backref='groups')


class Server(Base):
    __tablename__ = 'server'

    id = Column(Integer, primary_key=True, autoincrement=True)
    hostname = Column(String(64), unique=True, nullable=False)


def init_db():
    """
    根據類建立數據庫表
    :return: 
    """
    engine = create_engine(
        "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
    )

    Base.metadata.create_all(engine)


def drop_db():
    """
    根據類刪除數據庫表
    :return: 
    """
    engine = create_engine(
        "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
    )

    Base.metadata.drop_all(engine)


if __name__ == '__main__':
    drop_db()
    init_db()
建立多個表幷包含Fk、M2M關係

b.、操做數據庫表架構

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Users
 
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
##############方式一########################
Session = sessionmaker(bind=engine)
 
# 每次執行數據庫操做時，都須要建立一個session
session = Session()
 
# ############# 執行ORM操做 #############
obj1 = Users(name="alex1")
session.add(obj1)
 
# 提交事務
session.commit()
# 關閉session
session.close()

######################方式二####################
# 方式二：支持線程安全，爲每一個線程建立一個session
# - threading.Local
# - 惟一標識
# ScopedSession對象
# self.registry(), 加括號 建立session
# self.registry(), 加括號 建立session
# self.registry(), 加括號 建立session
from greenlet import getcurrent as get_ident

Session = sessionmaker(bind=engine)

session = scoped_session(Session,get_ident)
# session.add
# 操做
session.remove()
View Code 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from db import Users

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)


def task(arg):
    session = Session()

    obj1 = Users(name="alex1")
    session.add(obj1)

    session.commit()


for i in range(10):
    t = threading.Thread(target=task, args=(i,))
    t.start()
多線程執行示例 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text

from db import Users, Hosts

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)

session = Session()

# ################ 添加 ################
"""
obj1 = Users(name="wupeiqi")
session.add(obj1)

session.add_all([
    Users(name="wupeiqi"),
    Users(name="alex"),
    Hosts(name="c1.com"),
])
session.commit()
"""

# ################ 刪除 ################
"""
session.query(Users).filter(Users.id > 2).delete()
session.commit()
"""
# ################ 修改 ################
"""
session.query(Users).filter(Users.id > 0).update({"name" : "099"})
session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False)
session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate")
session.commit()
"""
# ################ 查詢 ################
"""
r1 = session.query(Users).all()
r2 = session.query(Users.name.label('xx'), Users.age).all()
r3 = session.query(Users).filter(Users.name == "alex").all()
r4 = session.query(Users).filter_by(name='alex').all()
r5 = session.query(Users).filter_by(name='alex').first()
r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all()
r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()
"""


session.close()
基本增刪改查示例 
#　條件
ret = session.query(Users).filter_by(name='alex').all()
ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()
ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()
ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all()
from sqlalchemy import and_, or_
ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()
ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all()
ret = session.query(Users).filter(
    or_(
        Users.id < 2,
        and_(Users.name == 'eric', Users.id > 3),
        Users.extra != ""
    )).all()


# 通配符
ret = session.query(Users).filter(Users.name.like('e%')).all()
ret = session.query(Users).filter(~Users.name.like('e%')).all()

# 限制
ret = session.query(Users)[1:2]

# 排序
ret = session.query(Users).order_by(Users.name.desc()).all()
ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()

# 分組
from sqlalchemy.sql import func

ret = session.query(Users).group_by(Users.extra).all()
ret = session.query(
    func.max(Users.id),
    func.sum(Users.id),
    func.min(Users.id)).group_by(Users.name).all()

ret = session.query(
    func.max(Users.id),
    func.sum(Users.id),
    func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()

# 連表

ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()

ret = session.query(Person).join(Favor).all()

ret = session.query(Person).join(Favor, isouter=True).all()


# 組合
q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Favor.caption).filter(Favor.nid < 2)
ret = q1.union(q2).all()

q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Favor.caption).filter(Favor.nid < 2)
ret = q1.union_all(q2).all()
經常使用操做 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text
from sqlalchemy.engine.result import ResultProxy
from db import Users, Hosts

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)

session = Session()

# 查詢
# cursor = session.execute('select * from users')
# result = cursor.fetchall()

# 添加
cursor = session.execute('insert into users(name) values(:value)',params={"value":'wupeiqi'})
session.commit()
print(cursor.lastrowid)

session.close()
原生SQL語句 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text
from sqlalchemy.engine.result import ResultProxy
from db import Users, Hosts, Hobby, Person

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)
session = Session()
# 添加
"""
session.add_all([
    Hobby(caption='乒乓球'),
    Hobby(caption='羽毛球'),
    Person(name='張三', hobby_id=3),
    Person(name='李四', hobby_id=4),
])

person = Person(name='張九', hobby=Hobby(caption='姑娘'))
session.add(person)

hb = Hobby(caption='人妖')
hb.pers = [Person(name='文飛'), Person(name='博雅')]
session.add(hb)

session.commit()
"""

# 使用relationship正向查詢
"""
v = session.query(Person).first()
print(v.name)
print(v.hobby.caption)
"""

# 使用relationship反向查詢
"""
v = session.query(Hobby).first()
print(v.caption)
print(v.pers)
"""

session.close()
基於relationship操做ForeignKey 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text
from sqlalchemy.engine.result import ResultProxy
from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)
session = Session()
# 添加
"""
session.add_all([
    Server(hostname='c1.com'),
    Server(hostname='c2.com'),
    Group(name='A組'),
    Group(name='B組'),
])
session.commit()

s2g = Server2Group(server_id=1, group_id=1)
session.add(s2g)
session.commit()


gp = Group(name='C組')
gp.servers = [Server(hostname='c3.com'),Server(hostname='c4.com')]
session.add(gp)
session.commit()


ser = Server(hostname='c6.com')
ser.groups = [Group(name='F組'),Group(name='G組')]
session.add(ser)
session.commit()
"""


# 使用relationship正向查詢
"""
v = session.query(Group).first()
print(v.name)
print(v.servers)
"""

# 使用relationship反向查詢
"""
v = session.query(Server).first()
print(v.hostname)
print(v.groups)
"""


session.close()
基於relationship操做m2m 
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text, func
from sqlalchemy.engine.result import ResultProxy
from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)
session = Session()

# 關聯子查詢
subqry = session.query(func.count(Server.id).label("sid")).filter(Server.id == Group.id).correlate(Group).as_scalar()
result = session.query(Group.name, subqry)
"""
SELECT `group`.name AS group_name, (SELECT count(server.id) AS sid 
FROM server 
WHERE server.id = `group`.id) AS anon_1 
FROM `group`
"""


# 原生SQL
"""
# 查詢
cursor = session.execute('select * from users')
result = cursor.fetchall()

# 添加
cursor = session.execute('insert into users(name) values(:value)',params={"value":'wupeiqi'})
session.commit()
print(cursor.lastrowid)
"""

session.close()
其餘

基本增刪改查補充

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text

from db import Users, Hosts

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)

session = Session()

# ################ 添加 ################
"""
obj1 = Users(name="wupeiqi")
session.add(obj1)

#批量添加
session.add_all([
    Users(name="wupeiqi"),
    Users(name="alex"),
    Hosts(name="c1.com"),
])
session.commit()
"""

# ################ 刪除 ################
"""
session.query(Users).filter(Users.id > 2).delete()
session.commit()
"""
# ################ 修改 ################
"""
session.query(Users).filter(Users.id > 0).update({"name" : "099"})
session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False) #字符串
session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate")  #數字
session.commit()
"""
# ################ 查詢 ################
"""
r1 = session.query(Users).all()
r2 = session.query(Users.name.label('xx'), Users.age).all()   #lable #as xx
r3 = session.query(Users).filter(Users.name == "alex").all()
r4 = session.query(Users).filter_by(name='alex').all()   #若是裏面寫條件就用filter_by,和上面filter查詢是一回事，只是一種不一樣的方式
r5 = session.query(Users).filter_by(name='alex').first()
r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all()  #查詢裏面若是有動態傳參的時候，吧它包在text裏面，:value,:name這樣的語法後面用.params來進行格式化
r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()  #上面的這個方式也能夠用這一種 ，直接能夠進行SQL語句的查詢
"""


session.close()
View Code

 

3、SQLAlchemy-Utils

一、因爲sqlalchemy中沒有提供choice方法，因此藉助SQLAlchemy-Utils組件提供的choice方法

import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from sqlalchemy.orm import relationship
from sqlalchemy_utils import ChoiceType

Base = declarative_base()
class Xuan(Base):
    __tablename__ = 'xuan'
    types_choices = (
        (1,'歐美'),
        (2,'日韓'),
        (3,'老男孩'),
    )
    id = Column(Integer,primary_key=True,autoincrement=True)
    name = Column(String(64))
    types = Column(ChoiceType(types_choices,Integer()))

    __table_args__ = {
        'mysql_engine':'Innodb',
        'mysql_charset':'utf8',
    }

engine = create_engine(
    "mysql+pymysql://root:123@127.0.0.1:3306/ttt2?charset=utf8",
    max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
    pool_size=5,  # 鏈接池大小
    pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
    pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
)

Base.metadata.create_all(engine)


查詢：
　　result_list = session.query(Xuan).all()
　　for item in result_list:
　　　　print(item.types.code,item.types.value)
View Code

二、scoped_session

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session
engine = create_engine(
        "mysql+pymysql://root:123@47.93.4.198:3306/ttt?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
)
SessionFactory = sessionmaker(bind=engine)
# 方式一：因爲沒法提供線程共享功能，全部在開發時要注意，在每一個線程中本身建立 session。
#         from sqlalchemy.orm.session import Session
#         本身具備操做數據庫的：'close', 'commit', 'connection', 'delete', 'execute', 'expire',.....
session = SessionFactory()

# print('原生session',session)
# 操做
session.close()


# 方式二：支持線程安全，爲每一個線程建立一個session
#               - threading.Local
#               - 惟一標識
# ScopedSession對象
#       self.registry(), 加括號 建立session
#       self.registry(), 加括號 建立session
#       self.registry(), 加括號 建立session
from greenlet import getcurrent as get_ident
session = scoped_session(SessionFactory,get_ident)
# session.add
# 操做
session.remove()
View Code

三、Flask-SQLAlchemy和Flask-Migrate 組件

四、Flask-SQLAlchemy：吧Flask和SQLAlchemy結合在一塊兒，粘合劑
    在__init__.py 文件中
        1 引入Flask-SQLAlchemy    中的SQLAlchemy，實例化了一個SQLAlchemy對象
        2 註冊Flask-SQLAlchemy：
            - 有兩種方式
                方式一： 在函數裏面，SQLAlchemy(app)  #若是想在其餘地方使用這種方式就很差使了
                方式二： 在全局：
                    db = SQLAlchemy(),
                    在函數裏面 db.init_app(app)  #調用init_app方法吧app放進去了
        3、導入models的類
        4、導入的類中繼承了db.model，其實本質上仍是繼承了Base類
        五、manage.py 建立數據庫表，能夠經過命令來建立。藉助Flask-Migrate組件來完成
五、Flask-Migrate：
    -舊5 被斃掉了：在manage.py裏面導入db,之後執行db.create_all()建立表，之後執行drop_all()刪除表
      這樣很差，咱們能夠和Flask-Migrate結合起來用
    -新5：Flask-Migrate
        - 安裝組件：pip install Flask-Migrate
        - 5.1 導入    
            from flask_migrate import Migrate, MigrateCommand
            from app import db, app
        - 5.2 migrate = Migrate(app,db) #建立實例
        - 5.3 建立命令
            manager.add_command("db",MigrateCommand)
        - 5.4 執行命令
            python manage.py db init  #只執行第一次
            python manage.py db migrate
            python manage.py db upgrade
    在執行命令以前,得先鏈接數據庫，他纔會知道吧表放在那裏，
View Code

四、詳說註冊SQLAlchemy的兩種方式

1）方式一

from flask_sqlalchemy import SQLAlchemy
from flask import FLask
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = \
    "mysql://root:12345@localhost/test"
db = SQLAlchemy(app)

 2）方式二：

from flask_sqlalchemy import SQLAlchemy
from flask import FLask
db = SQLAlchemy()

def create_app():
    app = Flask(__name__)
    db.init_app(app)
    return app

五、操做數據庫

經過上面註冊了SQLAlchemy，就直接能夠從db.session了

#方式一
        db.session  #會自動建立一個session
        db.session.add()
        db.session.query(models.User.id,models.User.name).all()
        db.session.commit()
        db.session.remove()
#方式二
        導入models
        models.User.query

六、flask中全部用到過的組件

全部用過的組件
    Flask
    鏈接數據庫的兩種操做
        要麼DBUtils：用於執行原生SQL的
            用本身的util裏面的sqlhelper來完成
        要麼SQLAlchemy：遵循他本身的語法來連接
            方式一：SQLAlchemy(app)這種方式有侷限性，若是我在其餘地方也得用到呢?能夠吧它寫到全局
            方式二：優勢，
                實例化一下：db = SQLAlchemy()
                註冊：
                    在settings裏面配置一下數據庫連接方式
                        SQLALCHEMY_DATABASE_URI = "mysql+pymysql://root:123@47.93.4.198:3306/s6?charset=utf8"
                        SQLALCHEMY_POOL_SIZE = 2
                        SQLALCHEMY_POOL_TIMEOUT = 30
                        SQLALCHEMY_POOL_RECYCLE = -1
                    Flask-SQLAlchemy： db.init_app(app)
            
    Flask-Session  #用於吧session保存在其餘地方
    Flask-Script  #生成命令
    Flask-Migrate   #數據庫遷移
    Flask-SQLAlchemy  #將Flask和SQLAlchemy很好的結合在一塊兒
        #本質、:每次操做數據庫就會自動建立一個session鏈接，完了自動關閉
    Blinker  #信號
    Wtforms  #FORM組件
    用到的組件和版本
        pip3 freeze  #獲取環境中全部安裝的模塊
        pip3 freeze > a.txt
        pip3 freeze > requirements.txt
        #pip3 install pipreqs  #幫你找到當前程序的全部模塊，而且自動生成 requirements.txt文件,寫入內容
        pipreqs ./  #根目錄
        
        之後別人給你一個程序，告知你一個文件夾須要安裝的組件：requirements.txt
             進入程序目錄：
                pip install -r requirements.txt #就會把設計到的全部的組件就會裝上 
        
        結構：
            app
                static
                templates
                views
                __init__.py
                models.py
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