[Python-checkins] peps: Strawman proposal for a flexible primitive to wait for one of a set of Futures.

[guido.van.rossum]

http://hg.python.org/peps/rev/827d116d0a35
changeset:   4621:827d116d0a35
user:        Guido van Rossum <guido at google.com>
date:        Tue Dec 18 21:40:17 2012 -0800
summary:
  Strawman proposal for a flexible primitive to wait for one of a set of Futures.

files:
  pep-3156.txt |  17 +++++++++++++----
  1 files changed, 13 insertions(+), 4 deletions(-)


diff --git a/pep-3156.txt b/pep-3156.txt
--- a/pep-3156.txt
+++ b/pep-3156.txt
@@ -536,7 +536,7 @@
 - ``writelines(iterable)``.  Equivalent to::
 
     for data in iterable:
-      self.write(data)
+        self.write(data)
 
 - ``write_eof()``.  Close the writing end of the connection.
   Subsequent calls to ``write()`` are not allowed.  Once all buffered
@@ -838,10 +838,10 @@
   caller (likely a transport) must then write code like this::
 
     try:
-      res = ev.sock_recv(sock, 8192)
+        res = ev.sock_recv(sock, 8192)
     except Future as f:
-      yield from sch.block_future(f)
-      res = f.result()
+        yield from sch.block_future(f)
+        res = f.result()
 
 - Do we need a larger vocabulary of operations for combining
   coroutines and/or futures?  E.g. in addition to par() we could have
@@ -852,6 +852,15 @@
   syntax).  Anyway, I think all of these are easy enough to write
   using ``Task``.
 
+  Proposal: ``f = yield from wait_one(fs)`` takes a set of Futures and
+  sets f to the first of those that is done.  (Yes, this requires an
+  intermediate Future to wait for.)  You can then write::
+
+    while fs:
+        f = tulip.wait_one(fs)
+        fs.remove(f)
+        <inspect f>        
+
 - Task or callback priorities?  (I hope not.)
 
 

-- 
Repository URL: http://hg.python.org/peps