Python in a Nutshell

Name

FieldStorage

Synopsis

class FieldStorage(keep_blank_values=0)

When your script instantiates a FieldStorage instance f, module cgi parses the query string, and/or standard input, as appropriate. You need not determine whether the client used the POST or GET method, as cgi hides the distinction. Your script must instantiate FieldStorage only once, since the instantiation may consume standard input.

An instance f of class FieldStorage is a mapping. f’s keys are the name attributes of the form’s controls. When keep_blank_values is true, f also includes controls whose values are blank strings. By default, f ignores such controls. f supplies methods f .has_key and f .keys, with normal mapping semantics. The value for each key n, f [ n ], can be either:

• A list of k FieldStorage instances, if name n occurs more than once in the form (k is the number of occurrences of n)

• A single FieldStorage instance, if name n occurs exactly once in the form

How often a name occurs in a form depends on HTML form rules. Groups of radio or checkbox controls share a name, but an entire group amounts to just one occurrence of the name.

Values in a FieldStorage instance are in turn FieldStorage instances, to let you handle nested forms. In practice, you don’t need such complications. For each nested instance, just access the value (and occasionally other attributes), ignoring potential nested-mapping aspects. Avoid type tests: module cgi can optimize, using instances of MiniFieldStorage, a lightweight signature-compatible ...