diff options
Diffstat (limited to 'Lib')
| -rw-r--r-- | Lib/copy.py | 12 | ||||
| -rw-r--r-- | Lib/test/test_copy.py | 19 |
2 files changed, 24 insertions, 7 deletions
diff --git a/Lib/copy.py b/Lib/copy.py index 089d101..497f21f 100644 --- a/Lib/copy.py +++ b/Lib/copy.py @@ -173,8 +173,10 @@ def deepcopy(x, memo=None, _nil=[]): "un(deep)copyable object of type %s" % cls) y = _reconstruct(x, rv, 1, memo) - memo[d] = y - _keep_alive(x, memo) # Make sure x lives at least as long as d + # If is its own copy, don't memoize. + if y is not x: + memo[d] = y + _keep_alive(x, memo) # Make sure x lives at least as long as d return y _deepcopy_dispatch = d = {} @@ -214,9 +216,10 @@ def _deepcopy_tuple(x, memo): y = [] for a in x: y.append(deepcopy(a, memo)) - d = id(x) + # We're not going to put the tuple in the memo, but it's still important we + # check for it, in case the tuple contains recursive mutable structures. try: - return memo[d] + return memo[id(x)] except KeyError: pass for i in range(len(x)): @@ -225,7 +228,6 @@ def _deepcopy_tuple(x, memo): break else: y = x - memo[d] = y return y d[tuple] = _deepcopy_tuple diff --git a/Lib/test/test_copy.py b/Lib/test/test_copy.py index a84c109..e450f70 100644 --- a/Lib/test/test_copy.py +++ b/Lib/test/test_copy.py @@ -321,9 +321,24 @@ class TestCopy(unittest.TestCase): def test_deepcopy_keepalive(self): memo = {} - x = 42 + x = [] + y = copy.deepcopy(x, memo) + self.assertIs(memo[id(memo)][0], x) + + def test_deepcopy_dont_memo_immutable(self): + memo = {} + x = [1, 2, 3, 4] y = copy.deepcopy(x, memo) - self.assertTrue(memo[id(x)] is x) + self.assertEqual(y, x) + # There's the entry for the new list, and the keep alive. + self.assertEqual(len(memo), 2) + + memo = {} + x = [(1, 2)] + y = copy.deepcopy(x, memo) + self.assertEqual(y, x) + # Tuples with immutable contents are immutable for deepcopy. + self.assertEqual(len(memo), 2) def test_deepcopy_inst_vanilla(self): class C: |