<pre> 
#!/usr/bin/python3
#####################################################################################
# Create and use a shopping cart (sample code)
# This shopping cart does not use cookies, session variables, nor database
# A cart is created using appName_IPaddr
#####################################################################################
import cgi
import cgitb
import shopcartFunc                                 #import custom shopCart functions

cgitb.enable()
 
print('Content-type: text/html \n')

appName = 'XYZ'                                     #enter a unique application name or leave it XYZ

elements  = cgi.FieldStorage()
option    = elements.getvalue('opt')      or ''     #get the button option pressed 
itemName  = elements.getvalue('item')     or ''     #from query string       
itemPrice = elements.getvalue('price')    or ''     #from query string      
itemQty   = elements.getvalue('quantity') or ''     #from input field
itemCmt   = elements.getvalue('comment')  or ''     #from input field

itemErr = ''
qtyErr  = ''
error   = ''
msg     = ''

#-- Validate --------------------------------------------------------------------------------
if option == 'add':                                     #validate input fields
    if not itemQty or int(itemQty) &lt;= 0:
        qtyErr  = '*'
        error   = 'Please enter quantity'
    if not itemName:
        itemErr = '*'
        error   = 'Please choose a shopping cart item and enter quantity'
if option == 'del':
     if not itemName:
        itemErr = '*'
        error   = 'Please choose a shopping cart item to delete'
           
#-- Process --------------------------------------------------------------------------------
if not error:                                           #if no validation errors
    shopcartFunc.accessCart(appName)                    #Create new or access existing shopping cart
    if option == 'add':                                 #add an item to shopping cart                        
        values = '$'+ str(itemPrice) +', '+ itemQty
        if itemCmt: values += ', '+ itemCmt
        shopcartFunc.setCartItem(itemName,values)
        msg = F"Item {itemName} added to your shopping cart"                      
    if option == 'del':                                 #delete an item from shopping cart
        shopcartFunc.delCartItem(itemName)                                                                    
        msg = F"Item {itemName} deleted from your shopping cart"                      
    if option == 'clear':                               #delete entire shopping cart 
        shopcartFunc.deleteCart()
        itemName  = ''
        itemPrice = ''                   
        msg = "Your shopping cart has been cleared"                      

#--- Display HTML Page ------------------------------------------------------------------------
print("""
    &lt;html>
    &lt;head>
    &lt;title>Shopping Cart Example&lt;/title>
    &lt;style>
        button           {width:110px; color:white; background-color:2C2C2C}
        #button2         {width:110px; color:white; background-color:green; height:30px}
        #table1 td       {border:1px solid black; width:120; background-color:lightgray; cursor:pointer} 
        #table1 td:hover {background-color:red; color:white} 
       .readonly         {background-color:lightgray; color:red; font:bold}
        span             {color:red}}
    &lt;/style> 
    &lt;/head>
    &lt;body bgcolor=lightyellow>
    &lt;img src=img/emptyCart.jpg id=swap style='position:absolute; top:40; right:10; width:300; height:300'>
    &lt;h2>Shop From the List of Products Below&lt;/h2>
    &lt;br>
""")

print(F"&lt;form method=post name=frm >")  

#--- Below data should come from a database table ------------------------------------------
print("""
    &lt;fieldset style='width:720px'>
    &lt;table id=table1 >
    &lt;tr>&lt;th>Choose Item
    &lt;td onClick="document.frm.item.value='Apples';   document.frm.price.value='1.49'"
        onMouseOver="document.getElementById('swap').src='img/Apples.jpg'">            Apples  $1.49&lt;/td> 
    &lt;td onClick="document.frm.item.value='Oranges';   document.frm.price.value='1.25'"
        onMouseOver="document.getElementById('swap').src='img/Oranges.jpg'">           Oranges $1.25&lt;/td> 
    &lt;td onClick="document.frm.item.value='Peaches';   document.frm.price.value='1.99'"
        onMouseOver="document.getElementById('swap').src='img/Peaches.jpg'">           Peaches $1.99&lt;/td>
    &lt;td onClick="document.frm.item.value='Bananas';   document.frm.price.value='0.99'"
        onMouseOver="document.getElementById('swap').src='img/Bananas.jpg'">           Bananas $0.99&lt;/td>
    &lt;td onClick="document.frm.item.value='Pears';     document.frm.price.value='1.79'"
        onMouseOver="document.getElementById('swap').src='img/Pears.jpg'">             ears   $1.79&lt;/td>
    &lt;tr>&lt;th>
    &lt;td onClick="document.frm.item.value='Potatoes';  document.frm.price.value='0.99'"
        onMouseOver="document.getElementById('swap').src='img/Potatoes.jpg'">          Potatoes  $0.99&lt;/td> 
    &lt;td onClick="document.frm.item.value='Tomatos';   document.frm.price.value='1.49'"
        onMouseOver="document.getElementById('swap').src='img/Tomatos.jpg'">           Tomatos   $1.49&lt;/td>  
    &lt;td onClick="document.frm.item.value='Spinach';   document.frm.price.value='2.29'"
        onMouseOver="document.getElementById('swap').src='img/Spinach.jpg'">           Spinach   $2.29&lt;/td>  
    &lt;td onClick="document.frm.item.value='Carrots';   document.frm.price.value='1.19'"
        onMouseOver="document.getElementById('swap').src='img/Carrots.jpg'">           Carrots   $1.19&lt;/td>  
    &lt;td onClick="document.frm.item.value='Cucumbers'; document.frm.price.value='1.29'"
        onMouseOver="document.getElementById('swap').src='img/Cucumbers.jpg'">         Cucumbers $1.29&lt;/td>
    &lt;tr>&lt;th>
    &lt;td onClick="document.frm.item.value='Milk';    document.frm.price.value='3.49'"
        onMouseOver="document.getElementById('swap').src='img/Milk.jpg'">              Milk    $3.49&lt;/td> 
    &lt;td onClick="document.frm.item.value='Yogurt';  document.frm.price.value='1.49'"
        onMouseOver="document.getElementById('swap').src='img/Yogurt.jpg'">            Yogurt  $1.49&lt;/td>  
    &lt;td onClick="document.frm.item.value='Cheese';  document.frm.price.value='5.99'"
        onMouseOver="document.getElementById('swap').src='img/Cheese.jpg'">            Cheese  $5.99&lt;/td>  
    &lt;td onClick="document.frm.item.value='Juice';   document.frm.price.value='2.99'"
        onMouseOver="document.getElementById('swap').src='img/Juice.jpg'">             Juice   $2.99&lt;/td>  
    &lt;td onClick="document.frm.item.value='Cookies'; document.frm.price.value='6.99'"
        onMouseOver="document.getElementById('swap').src='img/Cookies.jpg'">           Cookies $6.99&lt;/td>
    &lt;/table>
""")

#--- Print form input fields -----------------------------------------------------------
print(F"""
    &lt;table>
    &lt;tr>&lt;td>                &lt;td> &lt;input type=text   name=item     value='{itemName}'  readonly class=readonly>                            &lt;span>{itemErr}&lt;/span> 
    &lt;tr>&lt;td>&lt;b>Item Price...&lt;td> &lt;input type=text   name=price    value='{itemPrice}' readonly class=readonly>           
    &lt;tr>&lt;td>&lt;b>Quantity.....&lt;td> &lt;input type=number name=quantity value='{itemQty}'> &lt;span>{qtyErr}&lt;/span> 
    &lt;tr>&lt;td>&lt;b>Comment..... &lt;td> &lt;textarea          name=comment  rows=4 cols=84>{itemCmt}&lt;/textarea> 
    &lt;/table>
    &lt;font color=red>{error} &nbsp&lt;/font>
    &lt;/fieldset>
    &lt;br>
    &lt;button type=submit name=opt value='add'>   Add Item    &lt;/button>
    &lt;button type=submit name=opt value='del'>   Delete Item &lt;/button>
    &lt;button type=submit name=opt value='view'>  View Cart   &lt;/button>
    &lt;button type=submit name=opt value='clear'> Clear Cart  &lt;/button>
    &lt;/form>
    &lt;button type=button id=button2 onclick="location.href='shopcheckout.py'"> Checkout &lt;/button>      &lt;!--redirect to another page-->
    &lt;font color=red> {msg} &lt;/font>
 """)

#--- Display Shopping Cart ---------------------------------------------------------------------
cartId    = shopcartFunc.getCartId() 
cartItems = shopcartFunc.getCartItems()                                 #get all items as a dictionary

if option=='view':                                                      #if option is view 
    if cartItems:    
        print(F"""&lt;h4>&lt;i>Cart Id:&lt;/i> {cartId} &lt;/h4> 
                  &lt;table border=2 bgcolor=tan>
                  &lt;tr bgcolor=cccccc>&lt;th>&lt;i>&lt;nobr>Item&lt;th width=500>&lt;i>Price & Quantity&lt;th>&lt;i>Delete&lt;/th>
              """)        
        for name in sorted(cartItems):                                  #loop thru the cart items
            print("&lt;tr>&lt;td>&lt;b>",name,"&lt;td width=500>",cartItems[name])  #print the item name & values
            print(F"&lt;td>&lt;a href=shop2.py?opt=del&item={name}>")       #anchor to current script
            print("&lt;img src=img/delete.png height=20 width=35>&lt;/a>")    #add delete button

        print("&lt;/table>")
    
    else:
        print("&lt;h4>Your Shopping Cart is Empty&lt;/h4>")
    
if cartItems: image = 'img/fullcart.jpg'
else:         image = 'img/emptycart.jpg'    
print(F"&lt;script>document.getElementById('swap').src='{image}'&lt;/script>") 


#=== link to see the python code =================================================
import os, sys
sys.path.insert(0,'/home/s/sultans/web/python/demo')
import zCode                          #import func to display the Python code
filename = os.path.abspath(__file__)  #get absolute file name 
zCode.display(filename)               #call it
#=================================================================================</pre>