Changing order of dictionaries keys based on preferred order

Question

The input is a dictionary, for example:

{'first_name':'Jane', 'occupation': 'astronaut', 'age':27, 'last_name':'Doe'}

The keys need to be rearranged to be in a specific order, given in a list, for example:

preferred_order = ['first_name', 'last_name', 'age', 'location']

The dictionary might not have all the keys in the preferred_order list, and might have keys that don't appear on the list.

In this specific case, the result of the sorting should be:

{'first_name':'Jane', 'last_name':'Doe', 'age':27, 'occupation': 'astronaut'}

Key location didn't get added to the dictionary, and the keys not in preferred_order are at the end.

@PranavHosangadi OK, sorry – eternal_student Jun 24 '21 at 19:34 — eternal_student, Jun 24 '21 at 19:34

score 1 · Accepted Answer · answered Jun 23 '21 at 15:20

Suggested algorithm:

Create a new, initially empty, dictionary;
Iterate through preferred_order: for every key in preferred_order, add key: value to the new dictionary if it exists in the old dictionary, and remove it from the old dictionary;
for every remaining key: value pair in the old dictionary, add it to the new dictionary.

For step 3, you can use dict.update or |=.

Further reading:

documentation on dict.update and |=;
more about |=;
How do I sort a dictionary by value?;
You can search for "sort dictionary by key" on stackoverflow, but be aware that most answers are outdated and recommend using collections.OrderedDict instead of dict, which is no longer necessary since Python 3.7.

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