title: check if a key exists in a bucket in s3 using boto3
body: <p>I would like to know if a key exists in boto3. I can loop the bucket contents and check the key if it matches.</p>
  
  <p>But that seems longer and an overkill. Boto3 official docs explicitly state how to do this. </p>
  
  <p>May be I am missing the obvious. Can anybody point me how I can achieve this.</p>