Reconstruct the list of dict in python but the result is not in order

Question

list_1 = [{'1': 'name_1', '2': 'name_2', '3': 'name_3',}, 
       {'1': 'age_1', '2': 'age_2' ,'3': 'age_3',}]

I want to manipulate this list so that the dicts contain all the attributes for a particular ID. The ID itself must form part of the resulting dict. An example output is shown below:

list_2 = [{'id' : '1', 'name' : 'name_1', 'age': 'age_1'},
       {'id' : '2', 'name' : 'name_2', 'age': 'age_2'},
       {'id' : '3', 'name' : 'name_3', 'age': 'age_3'}]

Then I did following:

>>> list_2=[{'id':x,'name':list_1[0][x],'age':list_1[1][x]} for x in list_1[0].keys()]

Then it gives:

>>> list_2
    [{'age': 'age_1', 'id': '1', 'name': 'name_1'}, 
     {'age': 'age_3', 'id': '3', 'name': 'name_3'}, 
     {'age': 'age_2', 'id': '2', 'name': 'name_2'}]

But I don't understand why 'id' is showing in the second position while 'age' showing first?

I tried other ways but the result is the same. Any one can help to figure it out?

I think this is quite the duplicate: http://stackoverflow.com/q/1867861/42346 — mechanical_meat, Aug 01 '16 at 04:12
python dictionaries has no order. you must you ordered dictionary — Marlon Abeykoon, Aug 01 '16 at 04:14

score 1 · Accepted Answer · answered Aug 01 '16 at 04:35

To keep the order, you should use an ordered dictionary. Using your sample:

new_list = [OrderedDict([('id', x), ('name', list_1[0][x]), ('age', list_1[1][x])]) for x in list_1[0].keys()]

Printing the ordered list...

for d in new_list:                                                                                            
    print(d[name], d[age])

name_1 age_1

name_3 age_3

name_2 age_2

score 0 · Answer 2 · edited May 23 '17 at 11:51

Try using an OrderedDict:

list_1 = [collections.OrderedDict([('1','name_1'), ('2', 'name_2'), ('3', 'name_3')]),
        collections.OrderedDict([('1','age_1'),('2','age_2'),('3', 'age_3')])]

list_2=[collections.OrderedDict([('id',x), ('name',list_1[0][x]), ('age', list_1[1][x])]) 
        for x in list_1[0].keys()]

This is more likely to preserve the order you want. I am still new to Python, so this may not be super Pythonic, but I think it will work.

output -

In [24]: list( list_2[0].keys() )
Out[24]: ['id', 'name', 'age']

Docs: https://docs.python.org/3/library/collections.html#collections.OrderedDict

Examples: https://pymotw.com/2/collections/ordereddict.html

Getting the constructors right: Right way to initialize an OrderedDict using its constructor such that it retains order of initial data?

Reconstruct the list of dict in python but the result is not in order

2 Answers2