Python redis模块详解

Posted 2020-11-22 cuisi

在使用 Redis、Codis 时，我们经常需要做一些批量操作，通过连接数据库批量对 key 进行操作：

常见的场景：

　　1.批量扫描key

　　2.获取info信息

　　3.获取client信息

　　4.设置配置参数

　　5.redis定期扫描

批量初始化redis 客户端：

 1 from redis import Redis
 2 def setExpiredKeys():
 3     try:
 4         if redis_pass == ‘none‘:
 5             redisclient = Redis(host=redis_host, port=redis_port,db=0)
 6         else:
 7             redisclient = Redis(host=redis_host, port=redis_port, password=redis_pass)
 8         # 初始化 redis 客户端：redisclient
 9         # info = redisclient.info()
10 
11     except Exception as e:
12         raise e
13 if __name__ == ‘__main__‘:
14     redis_host = ‘39.196.9.99‘
15     redis_port = 6001
16     redis_pass = ‘123456‘
17     setExpiredKeys()

 

详解：

1. Redis.info() 源代码：

　　返回结果：包含相关信息的字典

1 def info(self, section=None):
2 """
3 Returns a dictionary containing information about the Redis server
4 """
5 if section is None:
6     return self.execute_command(‘INFO‘)
7 else:
8     return self.execute_command(‘INFO‘, section)

1 info = redisclient.info()            # 返回 Redis Server Info的所有信息
2 info = redisclient.info(‘Keyspace‘)  # 返回指定section的信息    

1 output:
2 {‘db0‘: {‘keys‘: 20005, ‘expires‘: 5322, ‘avg_ttl‘: 84036169}}

 

2. Redis.get() 源代码

　　获取key的value

1 def get(self, name):
2         """
3         Return the value at key ``name``, or None if the key doesn‘t exist
4         """
5         return self.execute_command(‘GET‘, name)

1 info = redisclient.get(‘name‘)     # 返回value：‘Jack‘

 

3. Redis.client_list() 源代码

 1 def client_list(self, _type=None):
 2         """
 3         Returns a list of currently connected clients.
 4         If type of client specified, only that type will be returned.
 5         :param _type: optional. one of the client types (normal, master,
 6          replica, pubsub)
 7         """
 8         "Returns a list of currently connected clients"
 9         if _type is not None:
10             client_types = (‘normal‘, ‘master‘, ‘replica‘, ‘pubsub‘)
11             if str(_type).lower() not in client_types:
12                 raise DataError("CLIENT LIST _type must be one of %r" % (
13                                 client_types,))
14             return self.execute_command(‘CLIENT LIST‘, b‘TYPE‘, _type)
15         return self.execute_command(‘CLIENT LIST‘)

1 info = redisclient.client_list()        # 获取client列表

1 output：
2 [
3 {‘id‘: ‘1319‘, ‘addr‘: ‘127.0.0.1:48670‘, ‘fd‘: ‘7‘, ‘name‘: ‘‘, ‘age‘: ‘5263‘, ‘idle‘: ‘444‘, ‘flags‘: ‘N‘, ‘db‘: ‘0‘, ‘sub‘: ‘0‘, ‘psub‘: ‘0‘, ‘multi‘: ‘-1‘, ‘qbuf‘: ‘0‘, ‘qbuf-free‘: ‘0‘, ‘obl‘: ‘0‘, ‘oll‘: ‘0‘, ‘omem‘: ‘0‘, ‘events‘: ‘r‘, ‘cmd‘: ‘client‘}, 
4 {‘id‘: ‘1329‘, ‘addr‘: ‘113.46.252.27:54863‘, ‘fd‘: ‘8‘, ‘name‘: ‘‘, ‘age‘: ‘1‘, ‘idle‘: ‘0‘, ‘flags‘: ‘N‘, ‘db‘: ‘0‘, ‘sub‘: ‘0‘, ‘psub‘: ‘0‘, ‘multi‘: ‘-1‘, ‘qbuf‘: ‘0‘, ‘qbuf-free‘: ‘32768‘, ‘obl‘: ‘0‘, ‘oll‘: ‘0‘, ‘omem‘: ‘0‘, ‘events‘: ‘r‘, ‘cmd‘: ‘client‘}
5 ]

 

4. Redis.config_ 配置参数相关源代码：

 1 def config_get(self, pattern="*"):
 2     "Return a dictionary of configuration based on the ``pattern``"
 3     return self.execute_command(‘CONFIG GET‘, pattern)
 4 
 5 def config_set(self, name, value):
 6     "Set config item ``name`` with ``value``"
 7     return self.execute_command(‘CONFIG SET‘, name, value)
 8 def config_rewrite(self):
 9     "Rewrite config file with the minimal change to reflect running config"
10     return self.execute_command(‘CONFIG REWRITE‘)

 

举例：内存扩容

1 info = redisclient.config_get(‘maxmemory‘)
2 info1 = redisclient.config_set(‘maxmemory‘,‘100MB‘)
3 info2 = redisclient.config_rewrite()

1 output：
2 info : {‘maxmemory‘: ‘104857600‘}
3 info1: True
4 info2: b‘OK‘

 

5. Redis.scan_iter() 源代码

 1 def scan_iter(self, match=None, count=None):
 2     """
 3     Make an iterator using the SCAN command so that the client doesn‘t
 4     need to remember the cursor position.
 5     ``match`` allows for filtering the keys by pattern
 6     ``count`` allows for hint the minimum number of returns
 7     """
 8     cursor = ‘0‘
 9     while cursor != 0:
10         cursor, data = self.scan(cursor=cursor, match=match, count=count)
11         for item in data:
12             yield item

1 redisclient.scan_iter(count=500):     # 每次扫描并返回500个key，

 

以上是Redis模块中常用的几个函数，能够有效提高工作效率！