bpo-14911: Corrected generator.throw() documentation (GH-32207)

Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>

Doc/howto/functional.rst

@@ -589,7 +589,7 @@ generator function.
 In addition to :meth:`~generator.send`, there are two other methods on
 generators:
 
-* :meth:`throw(type, value=None, traceback=None) <generator.throw>` is used to
+* :meth:`throw(value) <generator.throw>` is used to
   raise an exception inside the generator; the exception is raised by the
   ``yield`` expression where the generator's execution is paused.
 

Doc/reference/datamodel.rst

@@ -2984,7 +2984,8 @@ generators, coroutines do not directly support iteration.
    :exc:`StopIteration`, or other exception) is the same as when
    iterating over the :meth:`__await__` return value, described above.
 
-.. method:: coroutine.throw(type[, value[, traceback]])
+.. method:: coroutine.throw(value)
+            coroutine.throw(type[, value[, traceback]])
 
    Raises the specified exception in the coroutine.  This method delegates
    to the :meth:`~generator.throw` method of the iterator that caused

Doc/reference/expressions.rst

@@ -561,14 +561,27 @@ is already executing raises a :exc:`ValueError` exception.
    could receive the value.
 
 
-.. method:: generator.throw(type[, value[, traceback]])
+.. method:: generator.throw(value)
+            generator.throw(type[, value[, traceback]])
 
-   Raises an exception of type ``type`` at the point where the generator was paused,
+   Raises an exception at the point where the generator was paused,
    and returns the next value yielded by the generator function.  If the generator
    exits without yielding another value, a :exc:`StopIteration` exception is
    raised.  If the generator function does not catch the passed-in exception, or
    raises a different exception, then that exception propagates to the caller.
 
+   In typical use, this is called with a single exception instance similar to the
+   way the :keyword:`raise` keyword is used.
+
+   For backwards compatability, however, the second signature is
+   supported, following a convention from older versions of Python.
+   The *type* argument should be an exception class, and *value*
+   should be an exception instance. If the *value* is not provided, the
+   *type* constructor is called to get an instance. If *traceback*
+   is provided, it is set on the exception, otherwise any existing
+   :attr:`~BaseException.__traceback__` attribute stored in *value* may
+   be cleared.
+
 .. index:: exception: GeneratorExit
 
 

Objects/genobject.c

@@ -410,8 +410,11 @@ gen_close(PyGenObject *gen, PyObject *args)
 
 
 PyDoc_STRVAR(throw_doc,
-"throw(typ[,val[,tb]]) -> raise exception in generator,\n\
+"throw(value)\n\
-return next yielded value or raise StopIteration.");
+throw(type[,value[,tb]])\n\
+\n\
+Raise exception in generator, return next yielded value or raise\n\
+StopIteration.");
 
 static PyObject *
 _gen_throw(PyGenObject *gen, int close_on_genexit,
@@ -1157,8 +1160,11 @@ PyDoc_STRVAR(coro_send_doc,
 return next iterated value or raise StopIteration.");
 
 PyDoc_STRVAR(coro_throw_doc,
-"throw(typ[,val[,tb]]) -> raise exception in coroutine,\n\
+"throw(value)\n\
-return next iterated value or raise StopIteration.");
+throw(type[,value[,traceback]])\n\
+\n\
+Raise exception in coroutine, return next iterated value or raise\n\
+StopIteration.");
 
 PyDoc_STRVAR(coro_close_doc,
 "close() -> raise GeneratorExit inside coroutine.");