using set for read_commands, thus make the lookup becomes O(1)

Author: kefu-reddit

rediscluster/client.py

@@ -172,7 +172,7 @@ class RedisCluster(Redis):
 
     # Not complete, but covers the major ones
     # https://redis.io/commands
-    READ_COMMANDS = [
+    READ_COMMANDS = set([
         "BITCOUNT",
         "BITPOS",
         "EXISTS",
@@ -212,7 +212,7 @@ class RedisCluster(Redis):
         "ZCOUNT",
         "ZRANGE",
         "ZSCORE"
-    ]
+    ])
 
     RESULT_CALLBACKS = dict_merge(
         string_keys_to_dict([