db.create_all() 'NoneType' 对象没有属性 'drivername' [英] db.create_all() 'NoneType' object has no attribute 'drivername'
问题描述
我正在使用 Python 和 Javascript 关注 CS50 的 Web 编程，在 Lecture4 中，我在尝试创建 postgresql 数据库表时遇到以下错误:
回溯(最近一次调用最后一次):文件create.py"，第 19 行，在 <module> 中主要的()文件create.py"，第 15 行，在主目录中db.create_all()文件/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py"，第963行，在create_all中self._execute_for_all_tables(app, bind, 'create_all')文件/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py"，第 955 行，在 _execute_for_all_tables操作(绑定=self.get_engine(应用程序，绑定)，**额外)文件/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py"，第896行，在get_engine返回connector.get_engine()文件/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py"，第556行，在get_engineself._sa.apply_driver_hacks(self._app，信息，选项)文件/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py"，第830行，在apply_driver_hacks如果 info.drivername.startswith('mysql'):AttributeError: 'NoneType' 对象没有属性 'drivername'我使用的代码在两个 python 文件中:第一个叫做models.py:
from flask_sqlalchemy import SQLAlchemydb = SQLAlchemy()班级飞行(db.Model):__tablename__ = "航班"id = db.Column(db.Integer, primary_key=True)origin = db.Column(db.String, nullable=False)目标 = db.Column(db.String, nullable=False)持续时间 = db.Column(db.Integer, nullable=False)类乘客(db.Model):__tablename__ = "乘客"id = db.Column(db.Integer, primary_key=True)名称 = db.Column(db.String, nullable=False)Flight_id = db.Column(db.Integer, db.ForeignKey("flight.id"), nullable=False)第二个文件叫做create.py:
导入操作系统从烧瓶导入烧瓶，render_template，请求从模型导入 *app = Flask(__name__)app.config["SQLALCHEMY_DATABASE_URI"] = os.getenv("postgresql://postgres:password@localhost/database1")app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = Falsedb.init_app(app)定义主():db.create_all()如果 __name__ == "__main__":使用 app.app_context():主要的()你能帮我吗?！
我认为这是您尝试连接到 Postgres 数据库的方式的问题:
app.config["SQLALCHEMY_DATABASE_URI"] = os.getenv("postgresql://postgres:password@localhost/database1")您可能希望此行改为以下内容:
app.config["SQLALCHEMY_DATABASE_URI"] = "postgresql://postgres:password@localhost/database1"因为 os.getenv(...) 当前正在尝试在您的系统上获取一个名为:"postgresql://postgres:password@localhost/database1" 并且您肯定没有使用此名称设置环境变量.这就是您的 postgres 驱动程序收到 NoneType 错误的原因:<块引用>
AttributeError: 'NoneType' 对象没有属性 'drivername'.
如果您想使用环境变量来获取数据库连接字符串，请在您的 .bash_profile 或 .bashrc 文件中执行如下操作:
export SQLALCHEMY_DATABASE_URI='postgresql://postgres:password@localhost/database1'然后将您的数据库连接代码更改为以下内容:
app.config["SQLALCHEMY_DATABASE_URI"] = os.environ.get('SQLALCHEMY_DATABASE_URI')希望这是有道理的！
I am following the CS50's Web Programming with Python and Javascript and in Lecture4 I have had the following error trying to create a postgresql database table:
Traceback (most recent call last):
File "create.py", line 19, in <module>
main()
File "create.py", line 15, in main
db.create_all()
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py", line 963, in create_all
self._execute_for_all_tables(app, bind, 'create_all')
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py", line 955, in _execute_for_all_tables
op(bind=self.get_engine(app, bind), **extra)
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py", line 896, in get_engine
return connector.get_engine()
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py", line 556, in get_engine
self._sa.apply_driver_hacks(self._app, info, options)
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/flask_sqlalchemy/__init__.py", line 830, in apply_driver_hacks
if info.drivername.startswith('mysql'):
AttributeError: 'NoneType' object has no attribute 'drivername'
The code that I have used is in two python file: The first 1 called models.py:
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
class Flight(db.Model):
__tablename__ = "flights"
id = db.Column(db.Integer, primary_key=True)
origin = db.Column(db.String, nullable=False)
destination = db.Column(db.String, nullable=False)
duration = db.Column(db.Integer, nullable=False)
class Passenger(db.Model):
__tablename__ = "passengers"
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String, nullable=False)
flight_id = db.Column(db.Integer, db.ForeignKey("flight.id"), nullable=False)
The second file is called create.py:
import os
from flask import Flask, render_template, request
from models import *
app = Flask(__name__)
app.config["SQLALCHEMY_DATABASE_URI"] = os.getenv("postgresql://postgres:password@localhost/database1")
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False
db.init_app(app)
def main():
db.create_all()
if __name__ == "__main__":
with app.app_context():
main()
Can you help me?!
I think this is an issue with how you're attempting to connect to your Postgres database:
app.config["SQLALCHEMY_DATABASE_URI"] = os.getenv("postgresql://postgres:password@localhost/database1")
you probably want this line to be the following instead:
app.config["SQLALCHEMY_DATABASE_URI"] = "postgresql://postgres:password@localhost/database1"
since the os.getenv(...) is currently trying to get an environment variable on your system named: "postgresql://postgres:password@localhost/database1" and you surely didn't set up an environment variable with this name.. Which is why you're getting a NoneType error for your postgres driver:
AttributeError: 'NoneType' object has no attribute 'drivername'.
If you want to use an environment variable to get your database connection string, do something like the following in your .bash_profile or .bashrc file:
export SQLALCHEMY_DATABASE_URI='postgresql://postgres:password@localhost/database1'
then change your database connection code to the following:
app.config["SQLALCHEMY_DATABASE_URI"] = os.environ.get('SQLALCHEMY_DATABASE_URI')
Hopefully that makes sense!
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