There are a number of built-in exceptions that represent warning
categories. This categorization is useful to be able to filter out
groups of warnings. The following warnings category classes are
currently defined:
Class
Description
Warning
This is the base class of all warning category
classes. It is a subclass of Exception.
UserWarning
The default category for warn().
DeprecationWarning
Base category for warnings about
deprecated features.
SyntaxWarning
Base category for warnings about dubious
syntactic features.
RuntimeWarning
Base category for warnings about dubious
runtime features.
FutureWarning
Base category for warnings about constructs
that will change semantically in the future.
PendingDeprecationWarning
Base category for warnings about
features that will be deprecated in the future (ignored by default).
ImportWarning
Base category for warnings triggered during the
process of importing a module (ignored by default).
UnicodeWarning
Base category for warnings related to Unicode.
While these are technically built-in exceptions, they are documented
here, because conceptually they belong to the warnings mechanism.
User code can define additional warning categories by subclassing one
of the standard warning categories. A warning category must always be
a subclass of the Warning class.
