Patch #1537 from Chad Austin

Change GeneratorExit's base class from Exception to BaseException

Doc/library/exceptions.rst

@@ -135,6 +135,13 @@ The following exceptions are the exceptions that are actually raised.
 
 .. exception:: GeneratorExit
 
+     Raise when a :term:`generator`\'s :meth:`close` method is called.  It
+     directly inherits from :exc:`BaseException` instead of :exc:`Exception` since
+     it is technically not an error.
+
+    .. versionchanged:: 3.0 
+       Changed to inherit from :exc:`BaseException`.
+
    Raise when a :term:`generator`\'s :meth:`close` method is called.
 
 

Doc/reference/expressions.rst

@@ -413,9 +413,6 @@ generator functions::
    ...         while True:
    ...             try:
    ...                 value = (yield value)
-   ...             except GeneratorExit:
-   ...                 # never catch GeneratorExit
-   ...                 raise
    ...             except Exception, e:
    ...                 value = e
    ...     finally:

Lib/test/exception_hierarchy.txt

 BaseException
  +-- SystemExit
  +-- KeyboardInterrupt
+ +-- GeneratorExit
  +-- Exception
-      +-- GeneratorExit
       +-- StopIteration
       +-- ArithmeticError
       |    +-- FloatingPointError

Lib/test/test_generators.py

@@ -1668,6 +1668,19 @@ And finalization:
 exiting
 
 
+GeneratorExit is not caught by except Exception:
+
+>>> def f():
+...     try: yield
+...     except Exception: print 'except'
+...     finally: print 'finally'
+
+>>> g = f()
+>>> g.next()
+>>> del g
+finally
+
+
 Now let's try some ill-behaved generators:
 
 >>> def f():

Misc/NEWS

@@ -245,6 +245,8 @@ Extension Modules
   * operator module: div, idiv, __div__, __idiv__, isCallable, sequenceIncludes
   * sys module: exc_clear(), exc_type, exc_value, exc_traceback
 
+- Issue #1537: Changed GeneratorExit's base class from Exception to BaseException.
+
 
 Library
 -------

Objects/exceptions.c

@@ -424,9 +424,9 @@ SimpleExtendsException(PyExc_Exception, StopIteration,
 
 
 /*
- *    GeneratorExit extends Exception
+ *    GeneratorExit extends BaseException
  */
-SimpleExtendsException(PyExc_Exception, GeneratorExit,
+SimpleExtendsException(PyExc_BaseException, GeneratorExit,
                        "Request that a generator exit.");