以对象为键对字典排序

Question

I'm pretty new to python and I'm trying to sort a dict which has some objects as keys.

I have a class Student(studID, name) which is the key of the dict and an array of grades that is the value of the dict.

This is what it looks like:

dictEx = {
   Student: [5,6],
   Student: [7,8],
   Student: [10,9]
}

That object Student has a method getName() to get the student name. What I'm trying to accomplish is to sort this dictionary first by the student name and then by the grades only if the students have the same name. (if I have two students named Andrew for example)

Answer 1

You have to create an instance of each class in the dictionary:

class Student:
   def __init__(self, *args):
      self.__dict__ = dict(zip(['name', 'grade'], args))
   def getName(self):
      return self.name
   def __repr__(self):
      return "{}({})".format(self.__class__.__name__, ' '.join('{}:{}'.format(a, b) for a, b in self.__dict__.items()))

dictEx = {
  Student('Tom', 10): [5,6],
  Student('James', 12): [7,8],
  Student('James', 7): [10,9],
}
new_dict = sorted(dictEx.items(), key=lambda x:(x[0].getName(), x[-1]))

Output:

[(Student(grade:12 name:James), [7, 8]), (Student(grade:7 name:James), [10, 9]), (Student(grade:10 name:Tom), [5, 6])]

Note, however, that dictionaries are unordered, so you will have to rely on a list of tuples, stored in new_dict , or use a collections.OrderedDict :

from collections import OrderedDict
d = OrderedDict()
new_dict = sorted(dictEx.items(), key=lambda x:(x[0].getName(), x[-1]))
for a, b in new_dict:
   d[a] = b