Python in a Nutshell

The warnings Module

Warnings are messages about errors or anomalies that may not be serious enough to be worth disrupting the program’s control flow (as would happen by raising a normal exception). The warnings module offers you fine-grained control over which warnings are output and what happens to them. Your code can conditionally output a warning by calling function warn in module warnings. Other functions in the module let you control how warnings are formatted, set their destinations, and conditionally suppress some warnings (or transform some warnings into exceptions).

Classes

Module warnings supplies several exception classes representing warnings. Class Warning subclasses Exception and is the base class for all warnings. You may define your own warning classes; they must subclass Warning, either directly or via one of its other existing subclasses, which are:

DeprecationWarning

Using deprecated features only supplied for backward compatibility

RuntimeWarning

Using features whose semantics are error-prone

SyntaxWarning

Using features whose syntax is error-prone

UserWarning

Other user-defined warnings that don’t fit any of the above cases

Objects

In the current version of Python, there are no concrete warning objects. A warning is composed of a message (a text string), a category (a subclass of Warning), and two pieces of information that identify where the warning was raised from: module (name of the module raising the warning) and lineno (line number of the source code ...