How to sort dictionaries of objects by attribute value?

Question

I would like to iterate over a dictionary of objects in an attribute sorted way

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)

This gives me the error message: AttributeError: 'str' object has no attribute 'age'

Solution 1

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

Solution 2

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

Comments

[Karl Knechtel]

You've missed the point. Iterating over a dict iterates over its keys. We are trying to sort the keys according to an attribute of the corresponding value.

[Karl Knechtel]

This iterates over the keys, according to the corresponding value's attribute. This may or may not be what you want; it isn't quite clear in the OP.

[Karl Knechtel]

This iterates over the values, sorted by the attribute. This may or may not be what you want; it isn't quite clear in the OP.

[Nolen Royalty]

@KarlKnechtel is definitely right that there's some ambiguity in the OP. I believe that this method should be faster than mine, although I do think sorting over the keys is slightly more clear.

[martineau]

@Karl: I think this is what the OP's looking for based on what they wrote.

[englishPete]

python 2.7 NameError: global name 'operator' is not defined