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When identifying things (such as host names) in the internet, it is often necessary to compare such identifications for ``equality''. Exactly how this comparison is executed may depend on the application domain, e.g. whether it should be case-insensitive or not. It may be also necessary to restrict the possible identifications, to allow only identifications consisting of ``printable'' characters.
RFC 3454 defines a procedure for ``preparing'' Unicode strings in
internet protocols. Before passing strings onto the wire, they are
processed with the preparation procedure, after which they have a
certain normalized form. The RFC defines a set of tables, which can be
combined into profiles. Each profile must define which tables it uses,
and what other optional parts of the stringprep procedure are
part of the profile. One example of a stringprep profile is
nameprep, which is used for internationalized domain names.
The module stringprep only exposes the tables from RFC
3454. As these tables would be very large to represent them as
dictionaries or lists, the module uses the Unicode character database
internally. The module source code itself was generated using the
mkstringprep.py utility.
As a result, these tables are exposed as functions, not as data structures. There are two kinds of tables in the RFC: sets and mappings. For a set, stringprep provides the ``characteristic function'', i.e. a function that returns true if the parameter is part of the set. For mappings, it provides the mapping function: given the key, it returns the associated value. Below is a list of all functions available in the module.
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