<pre> 
#!/usr/bin/env python3
#=====================================================================================
# Retrieve a URL from the web 
#=====================================================================================
import cgi                                    #import cgi module
import urllib.request                         #urllib.request module allows fetching of urls 
import cgitb
cgitb.enable()

print("Content-Type: text/html \n")           #required http response header (w/ extra line)

elements = cgi.FieldStorage()                 #obtain the http for elements

url = elements.getvalue('url') or "https://"  #entry field             
 
msg = ''                                      #global variable

#-------------------------------------------------------------------------------------
# Function to validate entry fields
#-------------------------------------------------------------------------------------
def validate():
    global msg                                #needed to modify global variable
                                              #no need if access to global is read only
    if url=='':
        msg = '*** Please enter URL ***'

#-------------------------------------------------------------------------------------
# Function to retrieve a URL from the web
#-------------------------------------------------------------------------------------
def getURL(url):
    global msg                                #needed to modify global variable

    url2 = url.replace(' ','%20')             #replace space with %20 

    try:
        resource = urllib.request.urlopen(url2)     #send the request
        page     = resource.read()                  #read the returned data as a bytes object
    except:
        msg  = "Could not retrieve URL"
        page = ""
       
    try:                                            #try
        page = page.decode()                        #decode the bytes object into a string
    except:                                         #if unsuccessful                                            
        pass                                        #do nothing                     
    
    return(page)
        
#-------------------------------------------------------------------------------------
# Function to display the page
#-------------------------------------------------------------------------------------
def display(page):
    global msg                             #needed to modify global variable
                                           #no need if access to blobal is read only
    print('''
        &lt;!DOCTYPE html>
        &lt;html>
        &lt;head>
        &lt;title>Get URL&lt;/title>
        &lt;style type="text/css">
            #Layer3 {position:relative; left:60px; top:10px; width:780px; height:110px;}
            .style4 {font-family: Arial, Helvetica, sans-serif; font-size:16px; font-weight: bold;}
            span    {font-weight:bold; cursor:pointer}
        &lt;/style>
        &lt;/head>
        &lt;body bgcolor='lightyellow'>
        &lt;div id='Layer3'>

        &lt;form METHOD=post ACTION=getURL.py>                
        &lt;fieldset style='width:750'>
        &lt;legend>Get a URL&lt;/legend> 

        &lt;table border='0'>
        &lt;tr>
        &lt;td> Location &lt;/td>
    ''')
    print("&lt;td>&lt;input type='text' id='url' name='url' size='75' value='" + url + "'>") 
    print(" include http(s)://")

    print(''' 
        &lt;/tr>
        &lt;tr>
        &lt;td>&lt;/td>
        &lt;td>&lt;input type='submit' value='  Retrieve  '>
    ''')
    print("&lt;font color='red'>" + msg + "&lt;/font>&lt;/td>")
    print('''
        &lt;/tr>
        &lt;/table>       
        &lt;/fieldset>
        &lt;/form>
        &lt;/div>
        &lt;i>Example:&lt;/i> 
        &lt;span onclick=document.getElementById('url').value=this.innerHTML>https://google.com&lt;/span>
        &lt;br>
        &lt;i>Example:&lt;/i> 
        &lt;span onclick=document.getElementById('url').value=this.innerHTML>https://workshop.sps.nyu.edu/~sultans/python/ &lt;/span>
        &lt;br>
        &lt;i>Example:&lt;/i> 
        &lt;span onclick=document.getElementById('url').value=this.innerHTML>https://workshop.sps.nyu.edu/~sultans/util/rest/REST.py?user=demo&pswd=demo&db=demo&sql=show tables &lt;/span>
        &lt;hr>
    ''')

    print(page)          #print the retrieved URL

#-------------------------------------------------------------------------------------
# Main code
#-------------------------------------------------------------------------------------

page = ''

if elements:                                    #if data was entered in the form 
    validate()                                  #validate entered data                            
    page = getURL(url)                          #retrieve the url

display(page)                                   #call display function


#=== link to see the python code ================================================
import os
import 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>