为什么我收到错误 404 - 尝试使用 Python Flask 时

Question

我一直在关注本教程： https://kb.objectrocket.com/postgresql/scrape-a-website-to-postgres-with-python-938

我的app.py文件看起来像这样（取自上面的教程）：

from flask import Flask  # needed for flask-dependent libraries below
from flask import render_template  # to render the error page
from selenium import webdriver  # to grab source from URL
from bs4 import BeautifulSoup  # for searching through HTML
import psycopg2  # for database access

# set up Postgres database connection and cursor.
t_host = "localhost" # either "localhost", a domain name, or an IP address.
t_port = "5432" # default postgres port
t_dbname = "scrape"
t_user = "postgres"
t_pw = "********"
db_conn = psycopg2.connect(host=t_host, port=t_port, dbname=t_dbname, user=t_user, password=t_pw)
db_cursor = db_conn.cursor()

app = Flask(__name__)


@app.route('/import_temp')
def import_temp():
    # set up your webdriver to use Chrome web browser
    my_web_driver = webdriver.Chrome("/usr/lib/chromium-browser/chromedriver")

    # designate the URL we want to scrape
    #   NOTE: the long string of characters at the end of this URL below is a clue that
    #   maybe this page is so dynamic, like maybe refers to a specific web session and/or day/time,
    #   that we can't necessarily count on it to be the same more than one time.
    #   Which means... we may want to find another source for our data; one that is more
    #   dependable. That said, whatever URL you use, the methodology in this lesson stands.
    t_url = "https://weather.com/weather/today/l/7ebb344012f0c5ff88820d763da89ed94306a86c770fda50c983bf01a0f55c0d"
    # initiate scrape of website page data
    my_web_driver.get("<a href='" + t_url + "'>" + t_url + "</a>")
    # return entire page into "t_content"
    t_content = my_web_driver.page_source
    # use soup to make page content easily searchable
    soup_in_bowl = BeautifulSoup(t_content)
    # search for the UNIQUE span and class for the data we are looking for:
    o_temp = soup_in_bowl.find('span', attrs={'class': 'deg-feels'})
    # from the resulting object, "o_temp", get the text parameter and assign it to "n_temp"
    n_temp = o_temp.text

    # Build SQL for purpose of:
    #    saving the temperature data to a new row
    s = ""
    s += "INSERT INTO tbl_temperatures"
    s += "("
    s += "n_temp"
    s += ") VALUES ("
    s += "(%n_temp)"
    s += ")"

    # Trap errors for opening the file
    try:
        db_cursor.execute(s, [n_temp, n_temp])
        db_conn.commit()
    except psycopg2.Error as e:
        t_msg = "Database error: " + e + "/n open() SQL: " + s
        return render_template("error_page.html", t_msg = t_msg)

    # Success!
    # Show a message to user.
    t_msg = "Successful scrape!"
    return render_template("progress.html", t_msg = t_msg)

    # Clean up the cursor and connection objects
    db_cursor.close()
    db_conn.close()

当我运行代码并转到http://127.0.0.1:5000时，我收到 404 错误消息：

Not Found
The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.

这是来自命令行的 output：

FLASK_APP = app.py
FLASK_ENV = development
FLASK_DEBUG = 0
In folder /home/lloyd/PycharmProjects/flaskProject
/home/lloyd/PycharmProjects/flaskProject/venv/bin/python -m flask run
 * Serving Flask app 'app.py' (lazy loading)
 * Environment: development
 * Debug mode: off
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [28/Dec/2021 08:25:01] "GET / HTTP/1.1" 404 -

我确实运行了一个成功的测试“Hello World”项目。

任何有关我收到此错误的原因的见解将不胜感激。

劳埃德

Answer 1

我认为您还没有看到您在问题中链接的整个教程。 它显然使用将两条路线指向一起的方法。

@app.route("/") # I think you have missed this.

# Set up Postgres database connection and cursor.
t_host = "PostgreSQL database host address" # either "localhost", a domain name, or an IP address.
t_port = "5432" # default postgres port
t_dbname = "database name"
t_user = "database user name"
t_pw = "password"
db_conn = psycopg2.connect(host=t_host, port=t_port, dbname=t_dbname, user=t_user, password=t_pw)
db_cursor = db_conn.cursor()

@app.route("/import_temp")    
def import_temp():

另外，请注意这可以组合在一起。

@app.route("/")
@app.route("/import_temp")
def import_temp():
    # Do something

Answer 2

首先打开终端，然后输入“ pip install flask ”，完成后按回车，然后输入“ import flask ”然后回车。 这将解决您的问题。