Python Standard Library

The exceptions Module

The exceptions module provides the standard exception hierarchy. It’s automatically imported when Python starts, and the exceptions are added to the _ _builtin_ _ module. In other words, you usually don’t need to import this module.

This is a Python module in 1.5.2, and a built-in module in 2.0 and later.

The following standard exceptions are defined by this module:

• Exception is used as a base class for all exceptions. It’s strongly recommended (but not yet required) that user exceptions are derived from this class too.

• SystemExit(Exception) is raised by the sys.exit function. If it propagates to the top level without being caught by a try-except clause, the interpreter is terminated without a traceback message.

• StandardError(Exception) is used as a base class for all standard exceptions (except SystemExit, that is).

• KeyboardInterrupt(StandardError) is raised when the user presses Control-C (or any other interrupt key). Note that this may cause strange errors if you use “catch all” try-except statements.

• ImportError(StandardError) is raised when Python fails to import a module.

• EnvironmentError is used as a base class for exceptions that can be caused by the interpreter’s environment (that is, they’re usually not caused by bugs in the program).

• IOError(EnvironmentError) is used to flag I/O-related errors.

• OSError(EnvironmentError) is used to flag errors by the os module.

• WindowsError(OSError) is used to flag Windows-specific errors from the ...