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Processing an XHTML form using CGI script

P: 3
I'm having problems casting input information from an XHTML form as a different type in a CGI script using Python.
For just a simple example I'd use the XHTML code:
[HTML]<?xml version = "1.0" encoding = "utf-8"?>
<!DOCTYPE html PUBLIC "-//w3c//DTD XHTML 1.1//EN"

<form action="./cgi-bin/" method="post">
Calculate:<br />
<input type="text" name="num1" /> + <input type="text" name="num2" /><br />
<input type="submit" value="Calculate" />

And the Python Code:

Expand|Select|Wrap|Line Numbers
  1. #!/usr/bin/env python
  3. import cgi
  4. import cgitb; cgitb.enable()
  6. def main():
  8.         form = cgi.FieldStorage()
  10.         num1 = form.getvalue("num1")
  11.         num2 = form.getvalue("num2")
  13.         sum = int(num1) + int(num2)
  15.         print "content-type:  text/html\n"
  17.         print "<?xml version = \"1.0\" encoding = \"utf-8\"?>"
  18.         print "<!DOCTYPE html PUBLIC \"-//w3c//DTD XHTML 1.1//EN\""
  19.         print "\"\">\n"
  20.         print "<html>"
  21.         print "  <head>"
  22.         print "    <title>Solution</title>"
  23.         print "    <style type=\"txt/css\">"
  24.         print "  <head>"
  25.         print "  <body>"
  27.         print "    <p>Solution: " + str(sum) + "</p>"
  29.         print "  </body>"
  30.         print "</html>"
  32. main()
However when I try to cast num1 and num2 as integers, I get an error saying that only string or number arguments can be used:

int() argument must be a string or a number

And if I don't cast them I get an error saying:

unsupported operand types for +: 'NoneType' and 'NoneType'

Is there a way to cast the input variables from the XHTML form as something other that 'NoneType' so that I can use them in calculations?
Dec 1 '06 #1
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2 Replies

Expert 5K+
P: 6,596
'NoneType' is the type of None.
Python converts many 'null' values to None (for example a SQL database item that is a null value gets returned in python as None). I appears to me (I don't read html) that there is no value in you form.
Dec 1 '06 #2

Expert 5K+
P: 6,596
A common practice is
Expand|Select|Wrap|Line Numbers
  1. try:
  2.     num1 = int(form.getvalue("num1"))
  3. except (TypeError, ValueError):
  4.     num1 = 0    # or warn the user somehow that the field is empty
Dec 1 '06 #3

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