title: TypeError: object of type 'numpy.int64' has no len() / TypeError: object of type 'int' has no len()/ while using classification_report in scikitlearn
body: <p>Sometimes when using sklearn.metrics.classification_report we get below error</p>
  <pre><code>TypeError: object of type 'int' has no len()
  </code></pre>
  <p>Sometime depending on the datatype we get error like below too</p>
  <pre><code>TypeError: object of type 'numpy.int64' has no len()
  </code></pre>
  <p>Sample code when we might get this error</p>
  <pre><code>t=pd.Series([1,2,3,4])
  p=np.asarray([1,2,3,4])
  target_names=[1,2,3,4]
  print(classification_report(t, p, target_names=target_names))
  </code></pre>