feat(stdlib): implement missing set update and pop methods

python/builtins.py

@@ -190,6 +190,29 @@ class set:
     def __contains__(self, elem):
         return elem in self._a
     
+    def pop(self):
+        if not self._a:
+            raise KeyError('pop from an empty set')
+        # dict.popitem() returns (key, value) tuple
+        k, _ = self._a.popitem()
+        return k
+
+    def difference_update(self, other):
+        for elem in other:
+            self.discard(elem)
+
+    def intersection_update(self, other):
+        to_remove = [elem for elem in self if elem not in other]
+        for elem in to_remove:
+            self.remove(elem)
+
+    def symmetric_difference_update(self, other):
+        for elem in other:
+            if elem in self:
+                self.remove(elem)
+            else:
+                self.add(elem)
+
     def __repr__(self):
         if len(self) == 0:
             return 'set()'

tests/470_set.py

@@ -87,4 +87,20 @@ assert not {1,2,3}.isdisjoint({2,3,4})
 
 # a = set()
 # b = {*a, 1, 2, 3, *a, *a}
-# assert b == {1, 2, 3}
+# assert b == {1, 2, 3}
+a = {1, 2, 3}
+b = a.pop()
+assert b in {1, 2, 3}
+assert len(a) == 2
+
+a = {1, 2, 3}
+a.difference_update({2, 3, 4})
+assert a == {1}
+
+a = {1, 2, 3}
+a.intersection_update({2, 3, 4})
+assert a == {2, 3}
+
+a = {1, 2, 3}
+a.symmetric_difference_update({2, 3, 4})
+assert a == {1, 4}