Custom Sorting Python Dictionary

Here is a dictionary object holding student name as key and student information as value

>>> studentDb = { 'sark' : { 'country' : 'india', 'mark' : 99 }, 'jack' : { 'country' : 'US', 'mark' : 98 },'guns' : { 'country' :  'netherlands', 'mark' : 94 }, 'rakes' : { 'country' : 'india', 'mark' : 93 } }

Printing the student names and their details by iterating the studentDb dictionary

>>> for student, details in studentDb.iteritems(): ...     print student, details ... sark {'country': 'india', 'mark': 98} rakes {'country': 'india', 'mark': 100} jack {'country': 'US', 'mark': 94} guns {'country': 'netherlands', 'mark': 99} >>>

You may notice that the iteration not returned the student details in the same order, that's in the dictionary.

Dictionaries in Python are unordered. Here is a solution to sort python dictionary object in custom order.

Solution:

>>> studentDb_sorted = sorted(studentDb.items(),      key=lambda i: studentList.index(i[0])) >>> for student, details in studentDb_sorted: ...     print student, details ...  sark {'country': 'india', 'mark': 98} jack {'country': 'US', 'mark': 94} guns {'country': 'netherlands', 'mark': 99} rakes {'country': 'india', 'mark': 100}

Output of the sorting method would return a list object with tuples. If you would like to have the output object as similar to dictionary, consider using the below method which uses OrderedDict

(or)

>>> from collections import OrderedDict >>> sorted_db = OrderedDict(sorted(studentDb.items(),      key=lambda i: studentList.index(i[0])))           >>> type(sorted_db) <class 'collections.OrderedDict'> >>> for student, details in sorted_db: ...     print student, details ...  sark {'country': 'india', 'mark': 98} jack {'country': 'US', 'mark': 94} guns {'country': 'netherlands', 'mark': 99} rakes {'country': 'india', 'mark': 100}