Flask的插件session、SQLAlchemy、Script、Migrate

一、flask-session

1、为什么要使用flask-session

因为flask默认的session是通过请求上下文放入到Local中的，是存在内存的，
而使用flask-session可以更改session存放的位置，
可以存放在redis、memcached、filesystem、mongodb、sqlalchemy等数据库中，
flask-session也是基于flask原本的session原理实现的，只是让session存放的位置更改了而已。

2、使用步骤

1. 下载  pip install flask-session
2. 导入  from flask-session import Session 到__init__的app实例里面
3. 更改配置文件
    class DevConfig(object):
        DEBUG = True
        SESSION_TYPE = "redis"
        SESSION_REDIS = redis.Redis(host="127.0.0.1", port="6379")
4. 实例化  Session(app)

3、Demo(使用蓝图搭建的Demo)

# 1. __init__.py
from flask import Flask
from FlaskPlug.views.user import userBlue  # 测试的视图
from flask_session import Session  # 导入插件flask-session


def create_app():
    app = Flask(__name__, template_folder='templates')
    # 更改配置信息
    app.config.from_object('settings.DevConfig')
    # 实例化
    Session(app)
    app.register_blueprint(userBlue)
    return app

__init__.py

# 2. settings.py
import redis


class DevConfig(object):
    DEBUG = True
    SESSION_TYPE = 'redis'
    SESSION_REDIS = redis.Redis(host='localhost', port=6379)

2. settings.py

# 3. user.py
from flask import Blueprint, session


userBlue = Blueprint("userBlue", __name__)


@userBlue.route('/')
def index():
    session['test'] = 'test-flask-session'
    return "index"


@userBlue.route("/user")
def user():
    print(session.get('test'))
    return "user"

3. user.py

二、Flask-SQLAlchemy

1、前戏

学习Flask-SQLAlchemy之前，我们先去学习一下SQLAlchemy(可看上一篇)，SQLAlchemy是一个Python的ORM框架，SQLAlchemy
而Flask-SQLAlchemy是基于SQLAlchemy实现的一个Flask插件。

2、使用步骤

1. 下载 pip install flask-sqlalchemy

2. 导入 from flask_sqlalchemy import SQLAlchemy

3. 在init.py 实例化 并且实现初始化

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
# SQLAlchemy必须在导入蓝图之前实例化
db = SQLAlchemy()
from FlaskPlug.views.user import userBlue


def create_app():
    app = Flask(__name__)
    # 导入配置信息
    app.config.from_object('settings.DevConfig')
    app.register_blueprint(userBlue)
    # 初始化db
    db.init_app(app)
    return app

4. 配置文件

# settings.py
class DevConfig(object):
    DEBUG = True
    
    # flask-SQLAlchemy配置
    # 连接什么数据库，哪个数据库
    SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:[email protected]:3306/sqlalchemy?charset=utf8'
    SQLALCHEMY_POOL_SIZE = 5
    SQLALCHEMY_MAX_OVERFLOW = 2
    SQLALCHEMY_TRACK_MODIFICATIONS = False

5. 建models

# 表必须继承flask-SQLAlchemy的SQLAlchemy的实例化对象db.Model
from FlaskPlug import db
# 其他一些字段的东西导入的是python的SQLAlchemy
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import relationship


class Book(db.Model):
    __tablename__ = 'book'

    id = Column(Integer, primary_key=True)
    title = Column(String(64), nullable=False)
    publisher_id = Column(Integer, ForeignKey('publisher.id'))
    publisher = relationship('Publisher', backref='books')
    tags = relationship('Tag', backref='books', secondary='book2tag')

    __table_args__ = (
        # UniqueConstraint联合唯一，这个联合唯一的字段名为：uni_id_name
        UniqueConstraint("id", "title", name="uni_id_title"),
        # 联合索引
        Index("id", "title")
    )

    def __repr__(self):
        return self.title


class Publisher(db.Model):
    __tablename__ = 'publisher'

    id = Column(Integer, primary_key=True)
    title = Column(String(64), nullable=False)

    def __repr__(self):
        return self.title


class Tag(db.Model):
    __tablename__ = 'tag'

    id = Column(Integer, primary_key=True)
    title = Column(String(64), nullable=False)

    def __repr__(self):
        return self.title


class Book2Tag(db.Model):
    __tablename__ = 'book2tag'

    id = Column(Integer, primary_key=True)
    book_id = Column(Integer, ForeignKey('book.id'))
    tag_id = Column(Integer, ForeignKey('tag.id'))

6. 生成表

# 需要使用app上下文
# 离线脚本这时候就体现作用了


from FlaskPlug import db, create_app
# 一定要导入models 否则找不到表创建不出来
from FlaskPlug.models import *


app = create_app()
# app_context()就是前两篇文章里面Flask请求上下文走过的流程啊
# app_ctx = AppContext(app)
app_ctx = app.app_context()
# with 就会去走AppContext的__enter__和__exit__方法
# __enter__就是去取app了，__exit__就是删除
with app_ctx:
    db.create_all()

注意：一般建表的py文件和生成表的py文件要分成两个文件执行，不然有时候会导致循环引用。
    

7. 基于flask-SQLAlchemy的ORM操作

跟python的SQLAlchemy一样的

@userBlue.route('/')
def index():
    # 给Tag增加一条数据
    tag_obj = Tag(title='python')
    db.session.add(tag_obj)
    db.session.commit()
    db.session.close()
    return "index"

8. Demo

# __init__.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
from FlaskPlug.views.user import userBlue


def create_app():
    app = Flask(__name__, template_folder='templates')
    app.config.from_object('settings.DevConfig')
    app.register_blueprint(userBlue)
    db.init_app(app)
    return app

__init__.py

# settings.py
class DevConfig(object):
    DEBUG = True
    # flask-SQLAlchemy配置
    SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:[email protected]:3306/sqlalchemy?charset=utf8'
    SQLALCHEMY_POOL_SIZE = 5
    SQLALCHEMY_MAX_OVERFLOW = 2
    SQLALCHEMY_TRACK_MODIFICATIONS = False

settings.py

# models.py
from FlaskPlug import db
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import relationship


class Book(db.Model):
    __tablename__ = 'book'

    id = Column(Integer, primary_key=True)
    title = Column(String(64), nullable=False)
    publisher_id = Column(Integer, ForeignKey('publisher.id'))
    publisher = relationship('Publisher', backref='books')
    tags = relationship('Tag', backref='books', secondary='book2tag')

    __table_args__ = (
        # UniqueConstraint联合唯一，这个联合唯一的字段名为：uni_id_name
        UniqueConstraint("id", "title", name="uni_id_title"),
        # 联合索引
        Index("id", "title")
    )

    def __repr__(self):
        return self.title


class Publisher(db.Model):
    __tablename__ = 'publisher'

    id = Column(Integer, primary_key=True)
    title = Column(String(64), nullable=False)

    def __repr__(self):
        return self.title


class Tag(db.Model):
    __tablename__ = 'tag'

    id = Column(Integer, primary_key=True)
    title = Column(String(64), nullable=False)

    def __repr__(self):
        return self.title


class Book2Tag(db.Model):
    __tablename__ = 'book2tag'

    id = Column(Integer, primary_key=True)
    book_id = Column(Integer, ForeignKey('book.id'))
    tag_id = Column(Integer, ForeignKey('tag.id'))

models.py

# run_models.py
from FlaskPlug import db, create_app
# 一定要导入models 否则找不到表创建不出来
from FlaskPlug.models import *


app = create_app()
# app_context()就是前两篇文章里面Flask请求上下文走过的流程啊
# app_ctx = AppContext(app)
app_ctx = app.app_context()
# with 就会去走AppContext的__enter__和__exit__方法
# __enter__就是去取app了，__exit__就是删除
with app_ctx:
    db.create_all()

run_models.py

# user.py
from flask import Blueprint, session
from FlaskPlug import db
from FlaskPlug.models import Tag, Book, Publisher


userBlue = Blueprint("userBlue", __name__)


@userBlue.route('/')
def index():
    # 给Tag增加一条数据
    tag_obj = Tag(title='python')
    db.session.add(tag_obj)
    db.session.commit()
    db.session.close()
    return "index"

user.py

# manager.py
from FlaskPlug import create_app


app = create_app()

if __name__ == '__main__':

    app.run()

manager.py

三、Flask-Script

1、下载安装

pip install flask-script

2、使用

1. manager.py下的代码
from FlaskPlug import create_app
from flask_script import Manager

app = create_app()
manager = Manager(app)

if __name__ == '__main__':
    # app.run()
    manager.run()


2. 启动命令
这样使用Manager后，我们就可以在Terminal中启动我们的项目
或者在cmd里面 cd到项目目录下启动也可以

启动命令变成
    1. 使用默认端口
    python manager.py runserver
    
    2. 自定义域名和端口
    python manager.py runserver -h 127.0.0.1 -p 8000

3、自定义命令

from FlaskPlug import create_app
from flask_script import Manager


app = create_app()
manager = Manager(app)


# 位置传参
@manager.command
def my_add(arg1, arg2):
    """
    自定义命令
    python manager.py my_add 1 2
    """
    ret = int(arg1) + int(arg2)
    print(arg1, arg2, ret)


# 关键字传参
# 关键字参数的简写：-n
# 关键字参数全写：--name
# 关键字的描述：dest
@manager.option('-n', '--name', dest='name')
@manager.option('-a', '--age', dest='age')
def person(name, age):
    """
    自定义命令
    执行： python manager.py person -n 小明 --age 28
    """
    print(name, age)


if __name__ == '__main__':
    # app.run()
    manager.run()

四、Flask-Migrate

1、下载

pip install flask-migrate

2、注意

flask-migrate依赖flask-script

3、使用

from FlaskPlug import create_app, db
from FlaskPlug.models import *
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand
# 1. 导入SQLAlchemy的实例化db和script、migrate插件


app = create_app()
manager = Manager(app)
Migrate(app, db)  # 2. 实例化Migrate


# 3. 给manager添加命令(MigrateCommand里面就存放了自定义的命令)
manager.add_command("db", MigrateCommand)

"""
数据库迁移命令
依赖 flask-script
python manager.py db init # 初始化
python manager.py db migrate # 相当于Django的ORM的makemigrations
python manager.py db upgrade # 相当于Django的ORM的migrate
"""


if __name__ == '__main__':
    # app.run()
    manager.run()