Why is this Python/PostgreSQL web scraping application not working?-CodePudding

I have been following this tutorial: https://kb.objectrocket.com/postgresql/scrape-a-website-to-postgres-with-python-938

My app.py file looks like this (taken from the above tutorial):

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

I have successfully imported the required libraries, and created a database to store the scraped data. However, when I run the application I receive the following error:

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)
[2021-12-29 18:14:58,672] ERROR in app: Exception on / [GET]
Traceback (most recent call last):
  File "/home/lloyd/PycharmProjects/flaskProject/venv/lib/python3.6/site-packages/flask/app.py", line 2073, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/lloyd/PycharmProjects/flaskProject/venv/lib/python3.6/site-packages/flask/app.py", line 1518, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/lloyd/PycharmProjects/flaskProject/venv/lib/python3.6/site-packages/flask/app.py", line 1516, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/lloyd/PycharmProjects/flaskProject/venv/lib/python3.6/site-packages/flask/app.py", line 1502, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File "/home/lloyd/PycharmProjects/flaskProject/app.py", line 33, in import_temp
    my_web_driver.get("<a href='"   t_url   "'>"   t_url   "</a>")
  File "/home/lloyd/PycharmProjects/flaskProject/venv/lib/python3.6/site-packages/selenium/webdriver/remote/webdriver.py", line 333, in get
    self.execute(Command.GET, {'url': url})
  File "/home/lloyd/PycharmProjects/flaskProject/venv/lib/python3.6/site-packages/selenium/webdriver/remote/webdriver.py", line 321, in execute
    self.error_handler.check_response(response)
  File "/home/lloyd/PycharmProjects/flaskProject/venv/lib/python3.6/site-packages/selenium/webdriver/remote/errorhandler.py", line 242, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.InvalidArgumentException: Message: invalid argument
  (Session info: chrome=96.0.4664.110)

127.0.0.1 - - [29/Dec/2021 18:14:58] "GET / HTTP/1.1" 500 -

I think that the web driver is unable to process the url: my_web_driver.get("<a href='" t_url "'>" t_url "</a>")

If anyone is able to let me an insight into why this is happening it would be greatly appreciated.

CodePudding user response：

This string

"<a href='"   t_url   "'>"   t_url   "</a>"

after variable substituation would result into a <tag> like structure as:

<a href='https://www.google.com/'>https://www.google.com/</a>

which isn't a valid url similar to the regular urls we need to pass through get(). As an example:

driver.get("https://www.google.com/")

Hence you see the error:

ERROR in app: Exception on / [GET]

Solution