def unique(iterable, key=None):
seen = set()
if key is None:
# Optimize the common case
for item in iterable:
if item in seen:
continue
seen.add(item)
yield item
else:
for item in iterable:
keyitem = key(item)
if keyitem in seen:
continue
seen.add(keyitem)
yield item
if __name__ == "__main__":
assert list(unique("abcd")) == list("abcd"), (list(unique("abcd")), "abcd".split())
assert list(unique("abca")) == list("abc")
assert list(unique("baaca")) == list("bac")
assert list(unique("")) == []
assert list(unique("to be or not to be".split())) == "to be or not".split()
assert list(unique("to be or not to be".split(), key=len)) == "to not".split()
assert list(unique(set("cabbage"))) == list(unique(set("cabbage")))
print("All tests passed.")
Diff to Previous Revision
--- revision 1 2011-06-23 09:54:39
+++ revision 2 2011-06-23 16:36:38
@@ -2,6 +2,7 @@
seen = set()
if key is None:
+ # Optimize the common case
for item in iterable:
if item in seen:
continue
