Simplify heapreplace() -- there's no need for an explicit test for

empty heap, since heap[0] raises the appropriate IndexError already.

Lib/heapq.py

@@ -150,13 +150,10 @@ def heapreplace(heap, item):
     returned may be larger than item!  That constrains reasonable uses of
     this routine.
     """
-
-    if heap:
-        returnitem = heap[0]
+    returnitem = heap[0]    # raises appropriate IndexError if heap is empty
     heap[0] = item
     _siftup(heap, 0)
     return returnitem
-    heap.pop()  # raise IndexError
 
 def heapify(x):
     """Transform list into a heap, in-place, in O(len(heap)) time."""