title: How to sort dictionaries of objects by attribute value?
body: <p>I would like to iterate over a dictionary of objects in an attribute sorted way </p>
  
  <pre><code>import operator
  
  class Student:
      def __init__(self, name, grade, age):
          self.name = name
          self.grade = grade
          self.age = age
  
  
  studi1 = Student('john', 'A', 15)
  studi2 = Student('dave', 'B', 10)
  studi3 = Student('jane', 'B', 12)
  
  student_Dict = {}
  student_Dict[studi1.name] = studi1
  student_Dict[studi2.name] = studi2
  student_Dict[studi3.name] = studi3
  
  for key in (sorted(student_Dict, key=operator.attrgetter('age'))):
      print(key)
  </code></pre>
  
  <p>This gives me the error message: <code>AttributeError: 'str' object has no attribute 'age'</code></p>