What is FieldStorage class in Python? Explain its usage.

1.	What is FieldStorage class in Python? Explain its usage.
Answer» FieldStorage class is defined in cgi module of Python’s standard library. A http server can be configured to run executable scripts and programs stored in the cgi-bin directory on the server and render response in HTML form towards client. For EXAMPLE a Python script can be executed from cgi-bin directory. However, the input to such a script may come from the client in the form of HTTP request either via its GET method or POST method. In following HTML script, a form with two text input elements are defined. User data is sent as a HTTP request to a script mentioned as parameter of ‘action’ attribute with GET method. <form action = "/cgi-bin/test.py" method = "get"> Name: <input type = "text" name = "name"> <br /> address: <input type = "text" name = "ADDR" /> <input type = "submit" VALUE = "Submit" /> </form> In order to process the user input, Python’s CGI script makes use of FieldStorage object. This object is actually a dictionary object with HTML form elements as key and user data as value. #!/usr/bin/python # Import CGI module import cgi # Create INSTANCE of FieldStorage fso = cgi.FieldStorage() The fso object now contains form data which can be retrieved using usual dictionary notation. nm = fso[‘name’] add=fso[‘addr’] FieldStorage class also defines the following methods: getvalue(): This method RETRIEVES value associated with form element. getfirst(): This method returns only one value associated with form field name. The method returns only the first value in case more values were given under such name. getlist():This method always returns a list of values associated with form field name.

Answer»

FieldStorage class is defined in cgi module of Python’s standard library.

A http server can be configured to run executable scripts and programs stored in the cgi-bin directory on the server and render response in HTML form towards client. For EXAMPLE a Python script can be executed from cgi-bin directory.

However, the input to such a script may come from the client in the form of HTTP request either via its GET method or POST method.

In following HTML script, a form with two text input elements are defined. User data is sent as a HTTP request to a script mentioned as parameter of ‘action’ attribute with GET method.

<form action = "/cgi-bin/test.py" method = "get"> Name: <input type = "text" name = "name"> <br /> address: <input type = "text" name = "ADDR" /> <input type = "submit" VALUE = "Submit" /> </form>

In order to process the user input, Python’s CGI script makes use of FieldStorage object. This object is actually a dictionary object with HTML form elements as key and user data as value.

#!/usr/bin/python # Import CGI module import cgi # Create INSTANCE of FieldStorage fso = cgi.FieldStorage()

The fso object now contains form data which can be retrieved using usual dictionary notation.

nm = fso[‘name’] add=fso[‘addr’]

FieldStorage class also defines the following methods:

getvalue(): This method RETRIEVES value associated with form element.
getfirst(): This method returns only one value associated with form field name. The method returns only the first value in case more values were given under such name.
getlist():This method always returns a list of values associated with form field name.

What is FieldStorage class in Python? Explain its usage.

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