title: How to get size of filtered objectsCollection in boto3
body: <p>I've tried the following to get the len/content_length of the <code>s3.Bucket.objectsCollection</code> in boto3 v1.7.37:</p>
  
  <pre><code>import boto3    
  s3 = boto3.resource('s3')
  bucket = s3.Bucket('myBucket')
  bucketObjects = bucket.objects.filter(Prefix='myPrefix')
  if (len(bucketObjects) &gt; 0):
       do_something()
  else:
       do_something_else()
  </code></pre>
  
  <p>Unfortunately this gives me the following error:</p>
  
  <pre><code>TypeError: object of type 's3.Bucket.objectsCollection' has no len()
  </code></pre>
  
  <p>I've also tried this with <code>bucketobjects.content_length</code> and got</p>
  
  <pre><code>AttributeError: 's3.Bucket.objectsCollection' object has no attribute 'content_length'
  </code></pre>
  
  <p>Am I going to have to iterate through the list and count the objects or is there a better way?</p>