Overview of the programs
from hashlib import sha256
from time import time
sid = sha256(repr(time()).encode()).hexdigest()
shelve module:
from shelve import open
session_store = open('sess_' + sid, writeback=True)
# Examples of writing to the file
session_store['firstname'] = 'Hugh'
session_store['surname'] = 'Jeegoh'
# Example of reading from the file
print(session_store.get('firstname'))
session_store.close()
Suppose our company Shrine of Bacchus Wines sell wines, listed in this database:
CREATE TABLE wines
(
wine_id INT AUTO_INCREMENT,
name VARCHAR(255) NOT NULL,
price DECIMAL(5, 2) NOT NULL,
PRIMARY KEY (wine_id)
);
show.catalog.py:#!/usr/local/bin/python3
from cgitb import enable
enable()
import pymysql as db
print('Content-Type: text/html')
print()
result = ''
try:
connection = db.connect('localhost', 'userid', 'password', 'database_name')
cursor = connection.cursor(db.cursors.DictCursor)
cursor.execute("""SELECT * FROM wines ORDER BY wine_id""")
result = """<table>
<tr><th colspan="3">Our Wines</th></tr>
<tr><th>Name</th><th>Price</th><th></th></tr>"""
for row in cursor.fetchall():
result += """<tr>
<td>%s</td>
<td>%s</td>
<td><a href="add_to_cart.py?wine_id=%s">Add to cart</a></td>
</tr>""" % (row['name'], row['price'], row['wine_id'])
result += '</table>'
cursor.close()
connection.close()
except db.Error:
result = '<p>Sorry! We are experiencing problems at the moment. Please call back later.</p>'
print("""<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>Shrine of Bacchus Wines</title>
</head>
<body>
%s
<p>
<a href="show_cart.py">Show cart</a>
</p>
</body>
</html>""" % (result))
add_to_cart.py:#!/usr/local/bin/python3
from cgitb import enable
enable()
from cgi import FieldStorage
from os import environ
from hashlib import sha256
from time import time
from shelve import open
from http.cookies import SimpleCookie
result = ''
try:
cookie = SimpleCookie()
http_cookie_header = environ.get('HTTP_COOKIE')
if not http_cookie_header:
sid = sha256(repr(time()).encode()).hexdigest()
cookie['sid'] = sid
else:
cookie.load(http_cookie_header)
if 'sid' not in cookie:
sid = sha256(repr(time()).encode()).hexdigest()
cookie['sid'] = sid
else:
sid = cookie['sid'].value
session_store = open('sess_' + sid, writeback=True)
# Get the id of the item being added to the cart
form_data = FieldStorage()
wine_id = form_data.getfirst('wine_id')
# If this item is not in the cart already, then quantity is 1; otherwise, increment the quantity.
qty = session_store.get(wine_id)
if not qty:
qty = 1
else:
qty +=1
session_store[wine_id] = qty
session_store.close()
print(cookie)
result = '<p>Item successfully added to your cart.</p>'
except IOError:
result = '<p>Sorry! We are experiencing problems at the moment. Please call back later.</p>'
print('Content-Type: text/html')
print()
print("""
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>Shrine of Bacchus Wines</title>
</head>
<body>
%s
<p>
<a href="show_cart.py">Show cart</a>
</p>
<p>
<a href="show_catalog.py">Show catalog</a>
</p>
</body>
</html>""" % (result))
show_cart.py:#!/usr/local/bin/python3
from cgitb import enable
enable()
from os import environ
from hashlib import sha256
from time import time
from shelve import open
from http.cookies import SimpleCookie
import pymysql as db
result = ''
try:
cookie = SimpleCookie()
http_cookie_header = environ.get('HTTP_COOKIE')
if not http_cookie_header:
sid = sha256(repr(time()).encode()).hexdigest()
cookie['sid'] = sid
else:
cookie.load(http_cookie_header)
if 'sid' not in cookie:
sid = sha256(repr(time()).encode()).hexdigest()
cookie['sid'] = sid
else:
sid = cookie['sid'].value
session_store = open('sess_' + sid, writeback=True)
if len(session_store) == 0:
result = '<p>No items in shopping cart.</p>'
else:
connection = db.connect('localhost', 'userid', 'password', 'database_name')
cursor = connection.cursor(db.cursors.DictCursor)
result = """<table>
<tr><th colspan="2">Your Cart</th></tr>
<tr><th>Wine</th><th>Quantity</th></tr>"""
for wine_id in session_store:
cursor.execute("""SELECT name FROM wines
WHERE wine_id = %s""", (wine_id))
row = cursor.fetchone()
result += '<tr><td>%s</td><td>%s</td></tr>' % (row['name'], session_store.get(wine_id))
result += '</table>'
cursor.close()
connection.close()
session_store.close()
print(cookie)
except (db.Error, IOError):
result = '<p>Sorry! We are experiencing problems at the moment. Please call back later.</p>'
print('Content-Type: text/html')
print()
print("""
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>Shrine of Bacchus Wines</title>
</head>
<body>
%s
<p>
<a href="show_catalog.py">Show catalog</a>
</p>
</body>
</html>""" % (result))