Issue #6690: Optimize the bytecode for expressions such as `x in {1, 2, 3}`,
where the right hand operand is a set of constants, by turning the set into
a frozenset and pre-building it as a constant. The comparison operation
is made against the constant instead of building a new set each time it is
executed (a similar optimization already existed which turned a list of
constants into a pre-built tuple). Patch and additional tests by Dave
Malcolm.
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index 9e8bb69..fcd7ccc 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -1,4 +1,5 @@
import dis
+import re
import sys
from io import StringIO
import unittest
@@ -115,6 +116,54 @@
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
],)
+ def test_folding_of_lists_of_constants(self):
+ for line, elem in (
+ # in/not in constants with BUILD_LIST should be folded to a tuple:
+ ('a in [1,2,3]', '(1, 2, 3)'),
+ ('a not in ["a","b","c"]', "(('a', 'b', 'c'))"),
+ ('a in [None, 1, None]', '((None, 1, None))'),
+ ('a not in [(1, 2), 3, 4]', '(((1, 2), 3, 4))'),
+ ):
+ asm = dis_single(line)
+ self.assertIn(elem, asm)
+ self.assertNotIn('BUILD_LIST', asm)
+
+ def test_folding_of_sets_of_constants(self):
+ for line, elem in (
+ # in/not in constants with BUILD_SET should be folded to a frozenset:
+ ('a in {1,2,3}', frozenset({1, 2, 3})),
+ ('a not in {"a","b","c"}', frozenset({'a', 'c', 'b'})),
+ ('a in {None, 1, None}', frozenset({1, None})),
+ ('a not in {(1, 2), 3, 4}', frozenset({(1, 2), 3, 4})),
+ ('a in {1, 2, 3, 3, 2, 1}', frozenset({1, 2, 3})),
+ ):
+ asm = dis_single(line)
+ self.assertNotIn('BUILD_SET', asm)
+
+ # Verify that the frozenset 'elem' is in the disassembly
+ # The ordering of the elements in repr( frozenset ) isn't
+ # guaranteed, so we jump through some hoops to ensure that we have
+ # the frozenset we expect:
+ self.assertIn('frozenset', asm)
+ # Extract the frozenset literal from the disassembly:
+ m = re.match(r'.*(frozenset\({.*}\)).*', asm, re.DOTALL)
+ self.assertTrue(m)
+ self.assertEqual(eval(m.group(1)), elem)
+
+ # Ensure that the resulting code actually works:
+ def f(a):
+ return a in {1, 2, 3}
+
+ def g(a):
+ return a not in {1, 2, 3}
+
+ self.assertTrue(f(3))
+ self.assertTrue(not f(4))
+
+ self.assertTrue(not g(3))
+ self.assertTrue(g(4))
+
+
def test_folding_of_binops_on_constants(self):
for line, elem in (
('a = 2+3+4', '(9)'), # chained fold