[Python-checkins] CVS: python/nondist/peps pep-0255.txt,1.6,1.7

[Tim Peters]

Update of /cvsroot/python/python/nondist/peps
In directory usw-pr-cvs1:/tmp/cvs-serv31571/peps

Modified Files:
	pep-0255.txt 
Log Message:
Added brief section about exception propagation.


Index: pep-0255.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0255.txt,v
retrieving revision 1.6
retrieving revision 1.7
diff -C2 -r1.6 -r1.7
*** pep-0255.txt	2001/06/19 20:11:50	1.6
--- pep-0255.txt	2001/06/20 19:08:20	1.7
***************
*** 170,173 ****
--- 170,203 ----
  
  
+ Generators and Exception Propagation
+ 
+     If an unhandled exception-- including, but not limited to,
+     StopIteration --is raised by, or passes through, a generator function,
+     then the exception is passed on to the caller in the usual way, and
+     subsequent attempts to resume the generator function raise
+     StopIteration.  In other words, an unhandled exception terminates a
+     generator's useful life.
+ 
+     Example (not idiomatic but to illustrate the point):
+ 
+     >>> def f():
+     ...     return 1/0
+     >>> def g():
+     ...     yield f()  # the zero division exception propagates
+     ...     yield 42   # and we'll never get here
+     >>> k = g()
+     >>> k.next()
+     Traceback (most recent call last):
+       File "<stdin>", line 1, in ?
+       File "<stdin>", line 2, in g
+       File "<stdin>", line 2, in f
+     ZeroDivisionError: integer division or modulo by zero
+     >>> k.next()  # and the generator function cannot be resumed
+     Traceback (most recent call last):
+       File "<stdin>", line 1, in ?
+     StopIteration
+     >>>
+ 
+ 
  Example