tasks a-s

Task/Power-set/Python/power-set-1.py

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+def list_powerset(lst):
+    # the power set of the empty set has one element, the empty set
+    result = [[]]
+    for x in lst:
+        # for every additional element in our set
+        # the power set consists of the subsets that don't
+        # contain this element (just take the previous power set)
+        # plus the subsets that do contain the element (use list
+        # comprehension to add [x] onto everything in the
+        # previous power set)
+        result.extend([subset + [x] for subset in result])
+    return result
+
+# the above function in one statement
+def list_powerset2(lst):
+    return reduce(lambda result, x: result + [subset + [x] for subset in result],
+                  lst, [[]])
+
+def powerset(s):
+    return frozenset(map(frozenset, list_powerset(list(s))))