Flask notes: 5: Database

The project folder needs to be assigned permissions under Linux and Mac, or it cannot be executed
The Flask-sqlalchemy extension is used in flask to manage program data.
Modifying a configuration file myblog/config.py

csrf_enabled=truesecret_key= ' you-will-never-guess ' Import osbasedir = Os.path.abspath (Os.path.dirname (__file__)) Sqlalchemy_database_uri = ' sqlite:///' + os.path.join (basedir, ' app.db ') Sqlalchemy_migrate_repo = Os.path.join ( Basedir, ' db_repository ') sqlalchemy_track_modifications=true#db file created in the same directory as the Create script # Sqlalchemy_database_uri is the Flask-sqlalchemy the required extensions. This is the path to our database file. # Sqlalchemy_migrate_repo is the folder used to store sqlalchemy-migrate database files. #SQLALCHEMY_TRACK_MODIFICATIONS not set to True will cause an error (seemingly no code will work)

Modifying the initialization script app/__init__.py

From flask import flaskfrom flask.ext.sqlalchemy import sqlalchemyapp=flask (__name__) app.config.from_object (' config ' Db=sqlalchemy (APP) from app import views,models# import flask-sqlalchemy# Create a DB object, this is our database # import a new module called Models

write the models module app/models.py

From app import Dbclass User (db. Model):    ID = db. Column (db. Integer, primary_key=true)    nickname = db. Column (db. String (+), Index=true, unique=true)    email = db. Column (db. String (+), Index=true, unique=true)    posts = db.relationship (' Post ', backref= ' author ', lazy= ' dynamic ')    def _ _repr__ (self):        return ' <user%r> '% (Self.nickname) class Post (db. Model):    ID = db. Column (db. Integer, Primary_key = True)    BODY = db. Column (db. String (    timestamp) = db. Column (db. DateTime)    user_id = db. Column (db. Integer, Db. ForeignKey (' user.id '))    def __repr__ (self):        return ' <post%r> '% (self.body)

Table relationships:
#数据模型类要继承db. Modeldb. Column () is the creation of a columndb. Integer is an integral typedb. string is of typePrimary_key = True is the primary keyIndex=true Adding Indexesunique=true full Table unique db.relationship (), the first argument is the class name, and the second backref name seems to be random (this parameter is user_id replaced with Authou when new data is added ), A third fixed lazy= ' dynamic ' db.relationship () define the contact of the primary key and the foreign keydb. ForeignKey () is a foreign keythe __repr__ method tells Python how to print a class object so that we can use it for debugging purposes.
Create a database mybolg/db_cj.py

From app import Dbdb.create_all () #create_all () is to create a database

executing this script will create the database
test new User xz_user.py

From app Import db, Modelsdef add_com (u):    db.session.add (U)    db.session.commit () U = models. User (nickname= ' John ', email= ' [email protected] ') add_com (u) w=models. User (nickname= ' Susan ', email= ' [email protected] ') add_com (w) #session. Add () adding data #session.commit () COMMIT Transaction

Test new article xz_body.py

Import Datetimefrom App Import db, MODELSU = models. User.query.get (1) p = models. Post (body= ' My first post! ', Timestamp=datetime.datetime.utcnow (), Author=u) Db.session.add (P) db.session.commit () # Authou is the user_id in the Post data Class (yes)

Test Query User cx_user.py

From app Import db, modelsusers = models. User.query.all () Print usersfor u in users:    print u.id,u.nicknamee=models. User.query.get (1) Print ep=models. User.query.filter_by (nickname= "John"). First () print P.idprint p.emaild=models. User.query.filter (models. User.email.endswith (' @email. com ')). All () Print D

Results:[<user u ' John ';, <user u ' Susan ';]1 John2 Susan<user u ' john ' >1[email protected][<user u ' John ';, <user u ' Susan ';]#query这个属性是查询, Query.all () is a query for all#query. Get () is the query primary key#filter_by () is a single filter condition, first () is selected#query. filter_by (Filter conditions). First () query the filter criteria#filter () multiple filter conditions
Test Query Article cx_body.py

From app Import db, MODELSU = models. User.query.get (1) Print uposts = U.posts.all () print postse=models. User.query.get (2) print E.posts.all ()

Results:<user u ' john ' >[<post u ' my first post! ' ;][  ]
test emptying the database db_qk.py

From app Import db, modelsusers = models. User.query.all () for u in Users:    db.session.delete (u) posts = models. Post.query.all () for p in posts:    Db.session.delete (P) db.session.commit () #session. Delete ()

Flask notes: 5: Database