Implement ZRANDMEMBER

Fix #192

fakeredis/commands_mixins/sortedset_mixin.py

@@ -3,6 +3,7 @@
 import functools
 import itertools
 import math
+import random
 from typing import Union, Optional
 
 from fakeredis import _msgs as msgs
@@ -414,5 +415,30 @@ def zmscore(self, key: CommandItem, *members: Union[str, bytes]) -> list[Optiona
         )
         return list(scores)
 
+    @command(name="ZRANDMEMBER", fixed=(Key(ZSet),), repeat=(bytes,))
+    def zrandmember(self, key: CommandItem, *args) -> list[Optional[float]]:
+        count, withscores = 1, None
+        if len(args) > 0:
+            count = Int.decode(args[0])
+        if len(args) > 1:
+            if casematch(b'withscores', args[1]):
+                withscores = True
+            else:
+                raise SimpleError(msgs.SYNTAX_ERROR_MSG)
+        zset = key.value
+        if zset is None:
+            return None if len(args) == 0 is None else []
+        if count < 0:  # Allow repetitions
+            res = random.choices(sorted(key.value.items()), k=-count)
+        else:  # Unique values from hash
+            count = min(count, len(key.value))
+            res = random.sample(sorted(key.value.items()), count)
+
+        if withscores:
+            res = [item for t in res for item in t]
+        else:
+            res = [t[0] for t in res]
+        return res
+
     def _encodefloat(self, value, humanfriendly):
         raise NotImplementedError  # Implemented in BaseFakeSocket

test/test_mixins/test_sortedset_commands.py

@@ -1079,3 +1079,15 @@ def test_zscan(r: redis.Redis):
         cursor, data = r.zscan(name, cursor, match='*7', count=6)
         results.update(data)
     assert results == {b'key:7': 7.0, b'key:17': 17.0}
+
+
+def test_zrandemember(r: redis.Redis):
+    r.zadd("a", {"a1": 1, "a2": 2, "a3": 3, "a4": 4, "a5": 5})
+    assert r.zrandmember("a") is not None
+    assert len(r.zrandmember("a", 2)) == 2
+    # with scores
+    assert len(r.zrandmember("a", 2, True)) == 4
+    # without duplications
+    assert len(r.zrandmember("a", 10)) == 5
+    # with duplications
+    assert len(r.zrandmember("a", -10)) == 10