CGI with Python

Question

I'm beginning to use CGI with Python.

After running the following piece of code:

#!c:\python34\python.exe

import cgi


print("Content-type: text/html\n\n") #important


def getData():
    formData = cgi.FieldStorage()
    InputUN = formData.getvalue('username')
    InputPC = formData.getvalue('passcode')
    TF = open("TempFile.txt", "w")
    TF.write(InputUN)
    TF.write(InputPC)
    TF.close()

if __name__ =="__main__":
    LoginInput = getData()
    print("cgi worked")

The following error occurs:

Traceback (most recent call last):
  File "C:\xampp\htdocs\actual\loginvalues.cgi", line 21, in <module>
    LoginInput = getData()
  File "C:\xampp\htdocs\actual\loginvalues.cgi", line 16, in getData
    TF.write(InputUN)
TypeError: must be str, not None
>>> 

I'm trying to write the values, inputted in html, to a text file.

Any help would be appreciated :)

Answer 1

Your calls to getValue() are returning None , meaning the form either didn't contain them, had them set to an empty string, or had them set by name only. Python's CGI module ignores inputs that aren't set to a non-null string.

Works for Python CGI:

• mysite.com/loginvalues.cgi?username=myname&pass=mypass

Doesn't work for Python CGI:

• mysite.com/loginvalues.cgi?username=&pass= (null value(s))
• mysite.com/loginvalues.cgi?username&pass (Python requires the = part.)

To account for this, introduce a default value for when a form element is missing, or handle the None case manually:

TF.write('anonymous' if InputUN is None else InputUN)
TF.write('password' if InputPC is None else InputUN)

As a note, passwords and other private login credentials should never be used in a URL. URLs are not encrypted . Even in HTTPS, the URL is sent in plain text that anyone on the network(s) between you and your users can read.

The only time a URL is ever encrypted is over a tunneled SSH port or an encrypted VPN, but you can't control that, so never bank on it.