"kj" wrote:
I suppose that I could write something like
def uniquify(items):
seen = set()
ret = []
for i in items:
if not i in seen:
ret.append(i)
seen.add(i)
return ret
But this seems to me like such a commonly needed operation that I
find it hard to believe one would need to resort to such self-rolled
solutions. Isn't there some more standard (and hopefully more
efficient, as in "C-coded"/built-in) approach?
The most "standard" way is a recipe from the itertools docs (I'd give a
link, but python.org is down at the moment):
def unique_everseen(iterable, key=None):
"List unique elements, preserving order. Remember all elements ever
seen."
# unique_everseen('AAAABBBCCDAABBB') --> A B C D
# unique_everseen('ABBCcAD', str.lower) --> A B C D
seen = set()
seen_add = seen.add
if key is None:
for element in iterable:
if element not in seen:
seen_add(element)
yield element
else:
for element in iterable:
k = key(element)
if k not in seen:
seen_add(k)
yield element
All the recipes mentioned there are pretty handy, so I've made a module
(iterutil.py) out of them.
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