What are the modules required for CGI programming in Python?

Python's cgi module is usually the starting place in writing CGI programs in Python. The main purpose of the cgi module is to extract the values passed to a CGI program from an HTML form. Mostly one interacts with CGI applications through an HTML form. One fills out some values in the form that specify details of the action to be performed, then call on the CGI to perform its action using your specifications.

You may include many input fields within an HTML form which can be of a number of different types (text, checkboxes, picklists, radio buttons, etc.).

Your Python script should begin with import cgi. The main thing done by the CGI module is to treat all the fields in the calling HTML form in a dictionary-like fashion. What you get is not exactly a Python dictionary, but it is easy to work with. Let's see an example −


import cgi
form = cgi.FieldStorage()   # FieldStorage object to
                            # hold the form data
# check whether a field called "username" was used...
# it might be used multiple times (so sep w/ commas)
if form.has_key('username'):
    username = form["username"]
    usernames = ""
    if type(username) is type([]):
        # Multiple username fields specified
        for item in username:
            if usernames:
                # Next item -- insert comma
                usernames = usernames + "," + item.value
                # First item -- don't insert comma
                usernames = item.value
        # Single username field specified
        usernames = username.value
# just for the fun of it let's create an HTML list
# of all the fields on the calling form
field_list = '<ul>\n'
for field in form.keys():
    field_list = field_list + '<li>%s</li>\n' % field
field_list = field_list + '</ul>\n'

We'll have to do more to present a useful page to the user, but we've made a good beginning by working on a submitting form.

Updated on: 16-Jun-2020


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