¿Cómo ordenar diccionarios de objetos por valor de atributo en python?

Question

me gustaría repetir un diccionario de objetos en un atributo ordenados manera

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) 

Esto me da el mensaje EROR: "AttributeError: objeto 'str' no tiene atributo 'edad'"

Answer 1

for student in (sorted(student_Dict.values(), key=operator.attrgetter('age'))): 
    print(student.name) 

Answer 2

Cómo se muestra en la documentación de sorted método

sorted(student_Dict.keys(), key=lambda student: student.age) 

Answer 3

>>> for key in sorted(student_Dict, key = lambda name: student_Dict[name].age): 
...  print key 
... 
dave 
jane 
john 

Answer 4

class Student: 
    def __init__(self, name, grade, age): 
      self.name = name 
      self.grade = grade 
      self.age = age 
    def __repr__(self): 
      return repr((self.name, self.grade, self.age)) 


student_objects = [ 
    Student('john', 'A', 15), 
    Student('jane', 'B', 12), 
    Student('dave', 'B', 10), 
] 
print student_objects 
student_objects.sort(key=attrgetter('age')) 
print student_objects 

source: https://wiki.python.org/moin/HowTo/Sorting