Idempotent cache key for function kwargs regardless of their order

memoization/caching/general/keys.py

@@ -8,8 +8,8 @@ def make_key(args, kwargs, kwargs_mark=(object(), )):
     key = args
     if kwargs:
         key += kwargs_mark
-        for item in kwargs.items():
-            key += item
+        for kwarg_key in sorted(kwargs.keys()):
+            key += (kwarg_key, kwargs[kwarg_key])
     try:
         hash_value = hash(key)
     except TypeError:  # process unhashable types

test.py

@@ -14,7 +14,7 @@
 lock = Lock()                     # for multi-threading tests
 random.seed(100)                  # set seed to ensure that test results are reproducible
 
-for i in range(1, 16):
+for i in range(1, 17):
     exec_times['f' + str(i)] = 0  # init to zero
 
 
@@ -115,6 +115,12 @@ def f15(x):
     return x
 
 
+@cached()
+def f16(*args, **kwargs):
+    exec_times['f16'] += 1
+    return list(args) + [(key, value) for (key, value) in kwargs.items()]
+
+
 ################################################################################
 # Test entry point
 ################################################################################
@@ -255,6 +261,39 @@ def test_memoization_statistic_only(self):
         self.assertEqual(info.misses, 0)
         self.assertEqual(info.current_size, 0)
 
+    def test_memoization_for_diffrent_order_of_kwargs(self):
+        f16(
+            1,
+            2,
+            kwarg1={"some": "dict"},
+            kwarg2=["it's", "a", "list"],
+            kwarg3="just_string",
+            kwarg4=4,
+        )
+        f16(
+            1,
+            2,
+            kwarg2=["it's", "a", "list"],
+            kwarg1={"some": "dict"},
+            kwarg4=4,
+            kwarg3="just_string",
+        )
+        f16(
+            1,
+            2,
+            kwarg3="just_string",
+            kwarg1={"some": "dict"},
+            kwarg4=4,
+            kwarg2=["it's", "a", "list"],
+        )
+
+        self.assertEqual(exec_times['f16'], 1)
+
+        info = f16.cache_info()
+        self.assertEqual(info.hits, 2)
+        self.assertEqual(info.misses, 1)
+        self.assertEqual(info.current_size, 1)
+
     def _general_test(self, tested_function, algorithm, hits, misses, in_cache, not_in_cache):
         # clear
         exec_times[tested_function.__name__] = 0