diff options
Diffstat (limited to 'Doc/library/exceptions.rst')
| -rw-r--r-- | Doc/library/exceptions.rst | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst index 5a7193393c..a428f5165f 100644 --- a/Doc/library/exceptions.rst +++ b/Doc/library/exceptions.rst @@ -170,8 +170,9 @@ The following exceptions are the exceptions that are usually raised. .. exception:: ImportError - Raised when an :keyword:`import` statement fails to find the module definition - or when a ``from ... import`` fails to find a name that is to be imported. + Raised when the :keyword:`import` statement has troubles trying to + load a module. Also raised when the "from list" in ``from ... import`` + has a name that cannot be found. The :attr:`name` and :attr:`path` attributes can be set using keyword-only arguments to the constructor. When set they represent the name of the module @@ -181,6 +182,14 @@ The following exceptions are the exceptions that are usually raised. .. versionchanged:: 3.3 Added the :attr:`name` and :attr:`path` attributes. +.. exception:: ModuleNotFoundError + + A subclass of :exc:`ImportError` which is raised by :keyword:`import` + when a module could not be located. It is also raised when ``None`` + is found in :data:`sys.modules`. + + .. versionadded:: 3.6 + .. exception:: IndexError @@ -228,9 +237,21 @@ The following exceptions are the exceptions that are usually raised. .. exception:: NotImplementedError This exception is derived from :exc:`RuntimeError`. In user defined base - classes, abstract methods should raise this exception when they require derived - classes to override the method. + classes, abstract methods should raise this exception when they require + derived classes to override the method, or while the class is being + developed to indicate that the real implementation still needs to be added. + + .. note:: + It should not be used to indicate that an operater or method is not + meant to be supported at all -- in that case either leave the operator / + method undefined or, if a subclass, set it to :data:`None`. + + .. note:: + + ``NotImplementedError`` and ``NotImplemented`` are not interchangeable, + even though they have similar names and purposes. See + :data:`NotImplemented` for details on when to use it. .. exception:: OSError([arg]) OSError(errno, strerror[, filename[, winerror[, filename2]]]) @@ -436,6 +457,15 @@ The following exceptions are the exceptions that are usually raised. Raised when an operation or function is applied to an object of inappropriate type. The associated value is a string giving details about the type mismatch. + This exception may be raised by user code to indicate that an attempted + operation on an object is not supported, and is not meant to be. If an object + is meant to support a given operation but has not yet provided an + implementation, :exc:`NotImplementedError` is the proper exception to raise. + + Passing arguments of the wrong type (e.g. passing a :class:`list` when an + :class:`int` is expected) should result in a :exc:`TypeError`, but passing + arguments with the wrong value (e.g. a number outside expected boundaries) + should result in a :exc:`ValueError`. .. exception:: UnboundLocalError |