The has_key opertor checks to see if a has contains a key. For example, let's consider a hash named "hash" that contains a key called "foo".

hash = {'foo': 'bar'}

An if else statement can be used to print text identifying if the hash contains a key named foo.

if hash.has_key('foo'):
  print("hash contains a key named foo")
else
  print("hash does not contain a key named foo")