expire a key not in redis

poc

1. if you expire a key not in redis

   1. not exist

       # False
       print conn.expire('not-exist-in-redis', 10)
      

   2. exist

       # True
       print conn.set('exist-in-redis', 'yeah')
       # True
       print conn.expire('exist-in-redis', 0)
       # None
       print conn.get('exist-in-redis')