Issue 2274: Add heapq.heappushpop().

1 files changed, 9 insertions, 2 deletions

diff --git a/Lib/heapq.py b/Lib/heapq.py
index 39e3800..23f5fcb 100644
--- a/Lib/heapq.py
+++ b/Lib/heapq.py
@@ -127,7 +127,7 @@ From all times, sorting has always been a Great Art! :-)
 """
 
 __all__ = ['heappush', 'heappop', 'heapify', 'heapreplace', 'merge',
-           'nlargest', 'nsmallest']
+           'nlargest', 'nsmallest', 'heappushpop']
 
 from itertools import islice, repeat, count, imap, izip, tee
 from operator import itemgetter, neg
@@ -165,6 +165,13 @@ def heapreplace(heap, item):
     _siftup(heap, 0)
     return returnitem
 
+def heappushpop(heap, item):
+    """Fast version of a heappush followed by a heappop."""
+    if heap and item > heap[0]:
+        item, heap[0] = heap[0], item
+        _siftup(heap, 0)
+    return item
+
 def heapify(x):
     """Transform list into a heap, in-place, in O(len(heap)) time."""
     n = len(x)
@@ -304,7 +311,7 @@ def _siftup(heap, pos):
 
 # If available, use C implementation
 try:
-    from _heapq import heappush, heappop, heapify, heapreplace, nlargest, nsmallest
+    from _heapq import heappush, heappop, heapify, heapreplace, nlargest, nsmallest, heappushpop
 except ImportError:
     pass