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python - 为什么当列确实存在时会出现列不存在错误？我正在修改 Flask 教程

问题描述

我有一个名为ticker_symbol 的列，但是当我运行没有这样的列的错误时出现错误。到目前为止，这是我的 auth.py 代码。它类似于 Flask 教程代码。我从 flaskr.company_database 模块获取我的 get_db 函数。我试图让用户在论坛中输入股票代码，我的 Python 代码将通过数据库查找该股票代码。还有更多代码，但没关系，因为我无法通过这部分代码。

import functools

from flask import (
    Blueprint, Flask, flash, g, redirect, render_template, request, session, url_for
)
from werkzeug.security import check_password_hash, generate_password_hash

from flaskr.company_database import get_db

#app = Flask(__name__)
bp = Blueprint('stock_search', __name__, url_prefix='/')

@bp.route('/', methods=('GET', 'POST'))
def enter_ticker_symbol():
    if request.method == 'POST': # The server accepts user input
        ticker_symbol = request.form['ticker_symbol'] # Returns Immutiable (Unchanged) Multi Dictionary
        company_database = get_db()
        error = None
        ticker_symbol = company_database.execute(
            'SELECT * FROM ticker_symbols WHERE ticker_symbol = ?', (ticker_symbol,)
        ).fetchone()

这是我的 companydatabase.py 文件

import sqlite3

import click
from flask import current_app, g
# g stores data that might need to be accessed by multiple functions during request
# current_app 
from flask.cli import with_appcontext

def get_db():
# Connects to a database
    if 'company_database' not in g:
        g.company_database = sqlite3.connect(
            current_app.config['DATABASE'],
            detect_types =  sqlite3.PARSE_DECLTYPES
        )
        g.company_database.row_factory = sqlite3.Row

    return g.company_database

这是我的 schema.sql 文件

DROP TABLE IF EXISTS ticker_symbols;

CREATE TABLE ticker_symbols (
  id INT PRIMARY KEY AUTOINCREMENT,
  ticker_symbol VARCHAR (10),
  company_name VARCHAR(255)
);

这是我的初始化文件

# This file contains application factory (whatever that means, provides structural foundation for flask app) and flaskr treated as package

import os

from flask import Flask


def create_app(test_config=None): # This function is known as the application factoryu
    # create and configure the app
    # Any configuration, registration, and other setup the application needs happens inside function
    app = Flask(__name__, instance_relative_config=True)
    # Creates flask instance
    # __name__ is name of current Python module
    # instance_relative_config=True shows configuration files are relative to instance folder
    # Instance folder is outside flaskr package and can hold local data that shouldn't be commited to version control
    # Examples of files that shouldnt be with version control, configuration secrets and database file
    app.config.from_mapping(
        SECRET_KEY='dev', # Temporary
        DATABASE=os.path.join(app.instance_path, 'flask.sqlite'),
        # SQLite database file is stored here.
    )

    if test_config is None:
        # load the instance config, if it exists, when not testing
        app.config.from_pyfile('config.py', silent=True)
        # The config.py file replaces the SECRET_KEY with real SECRET_KEY
    else:
        # load the test config if passed in
        app.config.from_mapping(test_config)
        # Use code from above (app.config.from_mapping)

    # ensure the instance folder exists
    try:
        os.makedirs(app.instance_path)
        # Does the app.instance path exist?
        # This is needed because the SQLite database file will be created there
        # Flask doesnt create instance folders automatically
    except OSError:
        pass

    from . import auth
    app.register_blueprint(auth.bp)

    from . import company_database
    company_database.init_app(app)
    
    return app

这是我的回溯

Traceback (most recent call last):
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 2463, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 2449, in wsgi_app
    response = self.handle_exception(e)
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 1866, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 2446, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 1951, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 1820, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 1949, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/nbosio1001/anaconda3/lib/python3.7/site-packages/flask/app.py", line 1935, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/nbosio1001/Documents/python/Fundamental_Analysis/selenium_python_small_sample_project/flask-tutorial/flaskr/auth.py", line 20, in enter_ticker_symbol
    'SELECT * FROM ticker_symbols WHERE ticker_symbol = ?', (ticker_symbol,)
sqlite3.OperationalError: no such column: ticker_symbol

标签： pythonsqliteflask

解决方案

当您更改架构时，再次运行该init-db命令以重新创建数据库。

$ flask init-db

替代执行

你能试试以下

ticker_symbol = company_database.execute(
            'SELECT * FROM ticker_symbols WHERE ticker_symbol=:my_selector', 
            {"my_selector": ticker_symbol}
        ).fetchone()

我认为您的变量ticker_symbol会导致问题。有关详细信息，请参见此处 (Python Doc)和此处 (sqlite3.OperationalError: no such column:)。

还要确保您实际上已经创建了您的表格，正如上面的评论所指出的那样。

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