Add key= argument to heapq.nsmallest() and heapq.nlargest().
diff --git a/Lib/heapq.py b/Lib/heapq.py
index b4ebb91..04725cd 100644
--- a/Lib/heapq.py
+++ b/Lib/heapq.py
@@ -129,7 +129,8 @@
__all__ = ['heappush', 'heappop', 'heapify', 'heapreplace', 'nlargest',
'nsmallest']
-from itertools import islice, repeat
+from itertools import islice, repeat, count, imap, izip, tee
+from operator import itemgetter
import bisect
def heappush(heap, item):
@@ -307,6 +308,33 @@
except ImportError:
pass
+# Extend the implementations of nsmallest and nlargest to use a key= argument
+_nsmallest = nsmallest
+def nsmallest(n, iterable, key=None):
+ """Find the n smallest elements in a dataset.
+
+ Equivalent to: sorted(iterable, key=key)[:n]
+ """
+ if key is None:
+ return _nsmallest(n, iterable)
+ in1, in2 = tee(iterable)
+ it = izip(imap(key, in1), count(), in2) # decorate
+ result = _nsmallest(n, it)
+ return map(itemgetter(2), result) # undecorate
+
+_nlargest = nlargest
+def nlargest(n, iterable, key=None):
+ """Find the n largest elements in a dataset.
+
+ Equivalent to: sorted(iterable, key=key, reverse=True)[:n]
+ """
+ if key is None:
+ return _nlargest(n, iterable)
+ in1, in2 = tee(iterable)
+ it = izip(imap(key, in1), count(), in2) # decorate
+ result = _nlargest(n, it)
+ return map(itemgetter(2), result) # undecorate
+
if __name__ == "__main__":
# Simple sanity test
heap = []