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What is the difference between GET and POST in Python CGI Programming?
In Python CGI Programming, the two primary methods for passing information from a web browser to a web server are GET and POST. Understanding their differences is crucial for web development security and functionality.
GET Method
The GET method sends encoded user information appended to the page request. The page and the encoded information are separated by the ? character as follows −
http://www.test.com/cgi-bin/hello.py?key1=value1&key2=value2
The GET method is the default method to pass information from browser to web server. It produces a long string that appears in your browser's Location box. Never use GET method if you have password or other sensitive information to pass to the server.
GET Method Limitations
- Size limitation: only 1024 characters can be sent in a request string
- Data is visible in the URL
- Not suitable for sensitive information
- Information is accessible through QUERY_STRING environment variable
Simple URL Example − GET Method
Here is a simple URL that passes two values to a CGI program using GET method ?
/cgi-bin/hello_get.py?first_name=ZARA&last_name=ALI
Below is the hello_get.py script to handle input given by web browser using the cgi module ?
#!/usr/bin/python3
# Import modules for CGI handling
import cgi, cgitb
# Create instance of FieldStorage
form = cgi.FieldStorage()
# Get data from fields
first_name = form.getvalue('first_name')
last_name = form.getvalue('last_name')
print("Content-type:text/html\r\n\r\n")
print("<html>")
print("<head>")
print("<title>Hello - CGI Program</title>")
print("</head>")
print("<body>")
print("<h2>Hello %s %s</h2>" % (first_name, last_name))
print("</body>")
print("</html>")
This would generate the following result ?
Hello ZARA ALI
HTML Form Example − GET Method
This example passes two values using HTML FORM and submit button ?
<form action = "/cgi-bin/hello_get.py" method = "get">
First Name: <input type = "text" name = "first_name"><br />
Last Name: <input type = "text" name = "last_name" />
<input type = "submit" value = "Submit" />
</form>
POST Method
The POST method is generally more reliable for passing information to a CGI program. It packages the information in the same way as GET methods, but instead of sending it as a text string after a ? in the URL, it sends it as a separate message through standard input.
POST Method Advantages
- No size limitations like GET method
- Data is not visible in the URL
- Suitable for sensitive information like passwords
- Data comes through standard input, not query string
CGI Script for POST Method
The same hello_get.py script handles both GET and POST methods seamlessly ?
#!/usr/bin/python3
# Import modules for CGI handling
import cgi, cgitb
# Create instance of FieldStorage
form = cgi.FieldStorage()
# Get data from fields (works for both GET and POST)
first_name = form.getvalue('first_name')
last_name = form.getvalue('last_name')
print("Content-type:text/html\r\n\r\n")
print("<html>")
print("<head>")
print("<title>Hello - CGI Program</title>")
print("</head>")
print("<body>")
print("<h2>Hello %s %s</h2>" % (first_name, last_name))
print("</body>")
print("</html>")
HTML Form Example − POST Method
The same form structure, but using POST method ?
<form action = "/cgi-bin/hello_get.py" method = "post">
First Name: <input type = "text" name = "first_name"><br />
Last Name: <input type = "text" name = "last_name" />
<input type = "submit" value = "Submit" />
</form>
Comparison
| Feature | GET Method | POST Method |
|---|---|---|
| Data Location | URL query string | HTTP request body |
| Size Limit | 1024 characters | No practical limit |
| Security | Data visible in URL | Data hidden from URL |
| Bookmarkable | Yes | No |
| Best Use | Search queries, navigation | Form submissions, sensitive data |
Conclusion
Use GET method for simple data retrieval and navigation where data visibility is not a concern. Use POST method for form submissions, sensitive data, or when dealing with large amounts of data. The cgi.FieldStorage() class handles both methods seamlessly in Python CGI programming.
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