flask related interview questions

2. Review 
   - wtforms 
   - SQLALchemy 
   
   Questions: 
      a. What does wtforms do? 
　　　　　　--Form validation, rendering labels 
      b. What knowledge points are involved in wtforms? Where is it used? 
         - metaclass 
　　　　　　　　is used to specify which class to use to create the current class --wtforms sort fields

　　　　　　　　metaclass--->class--->instance 
         -encapsulation: 
　　　　　　　　wtforms--UnboundField 
　　　　　　　　restframework--request 
         - __new__ 
　　　　　　　　wtforms--instantiation process-field instantiation returns: not StringField, but UnboundField

　　　　　　　　restframework--many=true 
　　　　　　　　singleton mode--class 
         method- __mro__ 
　　　　　　　　class inheritance order- 
         setattr 
　　　　　　　　cbv, django configuration file, wtforms instantiation: setattr(self, name, field)

         - type(...) 
　　　　　　　　type creates class 
      c. ORM and native SQL comparison? 
          ORM is simple to operate, and the development efficiency is fast. 
　　　　　　The native SQL operation is complex, and the database execution efficiency is fast 
      . d. What ORM frameworks have you used?　　
　　　　　　djangoORM 
　　　　　　SQLAlchemy

e. SQLAlchemy 
   - database connection pool 
   - native SQL 
   - ORM 
      - table operation 
         - default value 
         - index (joint index, if you want to hit the "leftmost prefix" rule) 
         - set table in sqlalchemy: 
            - engine 
            - encoding 
      - record operation 
         - CRUD