title: How to remove all elements in Redis
body: <p>How to remove all elements in Redis? I tried with the following snippet code from <a href="https://stackoverflow.com/a/52292379/3702377">this post</a> but didn't work.</p>
  
  <p>I've such this:</p>
  
  <pre><code>import redis
  from pprint import pprint
  
  cli = redis.Redis('localhost')
  
  dict_ = {  # dummy
      'tags': {'module': 'voltage', 'station': 'SNMP'},
      'metric_name': 'voltage',
      'value': 222,
      'time': '2018-11-13T15:25:09'
  }
  cli.hmset("pythonDict", dict_)
  
  for key in cli.keys('prefix:*'):  # Didn't work.
      cli.delete(key)
  
  pprint(cli.hgetall("pythonDict"))
  </code></pre>
  
  <p>Still, the previous data appeared from <code>dict_</code>. </p>