Flask详解(下篇)

男娘i 2023-08-17 16:22 50阅读 0赞

## 一 上下文管理 ##

当前请求到来时Flask处理的流程图：

![1293898-20190711181727672-417275996.png][]

### 当一个请求到来时： ###

请求到来之后uwsgi会触发app的\_\_call\_\_方法， 由\_\_call\_\_方法再次调用wsgi\_app方法

![1293898-20190711182326147-710228687.png][]

首先将请求相关+空session封装到一个RequestContext对象中 即 ctx \# self是app对象, environ请求相关的原始数据，含有self.request

![1293898-20190711182503267-1166405048.png][]

通过ctx.push()将ctx交给LocalStack对象，再由LocakStack将ctx添加到Local中，local结构：

__storage__={
            1231:{stack:[ctx,]}，  # {线程id：{"stack":[]}}
            1232:{stack:[ctx,]}
    }

![1293898-20190712182346774-42993418.png][]

![1293898-20190711183543947-547661731.png][]

![1293898-20190712182816129-1160466822.png][]

当执行视图函数导入request模块后 执行\_lookup\_req\_object偏函数,传递request或者session

![1293898-20190712181110435-1247535003.png][]

\_request\_ctx\_stack.top取出stack中最后一个数据并使用getattr(obj,name)的方式返回request或者seession中的数据

**top相当于取出来的ctx， name为偏函数传递的request或者session**

![1293898-20190712181313650-2018227059.png][]

**top的执行过程**

![1293898-20190711183727060-1515015812.png][]

![1293898-20190711184211931-985617221.png][]

当我们使用request.method 调用LocalProxy中的\_\_getattr\_\_方法取出method中的数据

**执行\_get\_curren\_object 执行self.\_\_local()然而\_\_local实际上就是我们的偏函数lookup\_req\_object(request)**

![1293898-20190712184505118-1275310580.png][]

![1293898-20190712190055085-892662973.png][]

## 二 flask-sqlalchemy ##

### 1 下载安装 ###

pip3 install flask-sqlalchemy

### 2 crm.\_\_init\_\_.py ###

导入并实例化SQLAlchemy  
from flask\_sqlalchemy import SQLAlchemy  
db = SQLAlchemy()  
注意事项：

*  必须在导入蓝图的上边
 *  必须导入models.py

### 3 初始化 ###

db.init_app(app)

### 4 在配置文件中写入配置 ###

SQLALCHEMY_DATABASE_URI = "mysql+pymysql://root:123456@127.0.0.1:3306/databasename?charset=utf8"
    SQLALCHEMY_POOL_SIZE = 10
    SQLALCHEMY_MAX_OVERFLOW = 5

### 5 创建models.py中的类(对应数据库的表) ###

from sqlalchemy.ext.declarative import declarative_base
    from sqlalchemy import Column
    from sqlalchemy import Integer,String,Text,Date,DateTime
    from sqlallchemy import create_engine
    from crm import db
    
    class Users(db.model):
        __tablename__ = 'users'
        id = Column(Integer, primary_key=True)
        name = Column(String(32), index=True, nullable=False)
        depart_id = Column(Integer)

### 6 生成表(使用app上下文) createtale.py ###

from crm import db,create_app        
    app = create_app()
    app_ctx = app.app_context() # app_ctx = app/g
    with app_ctx: # __enter__,通过LocalStack放入Local中
        db.create_all()

### 7 基于sqlalchemy生成数据 ###

def index():
        db.session.add(models.User(name='harry', depart_id=1))
        db.session.commit()
        db.session.remove()

## 三 flask-script ##

flask-script功能类似于Django的manage，可以通过命令行的方式对项目进行管理

安装：pip3 install flask-script

### 1 增加 runserver ###

from crm import create_app
    from flask_script import Manager
    
    app = create_app()
    manager = Manager(app)
    
    if __name__ == '__main__':
        manager.run()

### 2 位置传参 ###

from crm import create_app
    from flask_script import Manager
    
    app = create_app()
    manager = Manager(app)
    
    @manager.command
    def custom(arg):
        '''
        自定义命令
        python manag.py custom 123
        '''
        print(arg)
        
        if __name__ == '__main__':
            manager.run()

### 3 关键字传参 ###

from crm import create_app
    from flask_script import Manager
    
    app = create_app()
    manager = Manager(app)
    
    @manager.option('-n', '--name', dest='name')
    @manager.option('-u', '--url', dest='url')
    def cmd(name, password):
        '''
        自定义命令
        执行 python manag.py cmd -n harry -u 123123
        '''
        print(name,password)
        
        
        if __name__ == '__main__':
            manager.run()

## 四 flask-migrate ##

通过命令行的方式生成数据库

安装： pip3 install flask-migrate

依赖：flask-script

from flask_script import Manager
    from flask_migrate import Migrate, MigrateCommand
    
    app = create_app()
    manager = Manager(app)
    Migrate(app, db)
    
    '''
    数据库迁移命令
        python manage.py db  init_app
        python manage.py db  migrate 
        python manage.py db  upgrate
    '''
    
    manager.add_command('db', MigrateCommand)
    if __name__ == '__main__':
        manager.run()

转载于:https://www.cnblogs.com/harryblog/p/11171831.html

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