Sorting list of dictionaries in python by day of week

Question

I have a list of dicts in python which look like these:

[{'day' : 'Wednesday' , 'workers' : ['John' , 'Smith']} , 
 {'day' : 'Monday' , 'workers' : ['Kelly']}]

I want to sort them by day of week such that the result is

[{'day' : 'Monday' , 'workers' : ['Kelly']},
 {'day' : 'Wednesday' , 'workers' : ['John' , 'Smith']}]

I can use this answer to sort list of just weekday names: Sort week day texts but is there a way to sort the above dict?

Does this answer your question? [How do I sort a dictionary by value?](https://stackoverflow.com/questions/613183/how-do-i-sort-a-dictionary-by-value) — Masklinn, Feb 18 '21 at 06:53
dicts are unsorted by nature.. why do u need to sort them in the first place.. what are u trying to achieve by sorting the dictionary? — Arun Kaliraja Baskaran, Feb 18 '21 at 06:54
@ArunKalirajaBaskaran they're trying to sort the list by one of the dict's keys, not trying to sort the dicts themselves. Your statement also has not been true for a while, Python dicts have been following / keeping insertion order since 3.6, and that's part of the language spec since 3.7. — Masklinn, Feb 18 '21 at 06:55

score 4 · Answer 1 · answered Feb 18 '21 at 07:02

The same basic approach that the example you link to uses will work for your list of dictionaries case. The trick is, you need to extract the day value from the dictionaries within the list to make it work. A lambda expression used for the key parameter is one way to do that.

Example:

day_order = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]
data = [{'day' : 'Wednesday' , 'workers' : ['John' , 'Smith']} , {'day' : 'Monday' , 'workers' : ['Kelly']}]

sorted(data, key=lambda d: day_order.index(d["day"]))

Output:

[{'day': 'Monday', 'workers': ['Kelly']},
 {'day': 'Wednesday', 'workers': ['John', 'Smith']}]

Barmar · Accepted Answer · 2021-02-18T07:19:42.203

2

Use a lambda function that extracts the weekday name from the dictionary and then returns the index as in your linked question.

weekdays = ["Mon", "Tue", "Wed", "Thu", "Fri"]
list_of_dicts = 
    [{'day' : 'Wednesday' , 'workers' : ['John' , 'Smith']} , 
     {'day' : 'Monday' , 'workers' : ['Kelly']}]
list_of_dicts.sort(key = lambda d: weekdays.index(d['day']))

edited Feb 18 '21 at 07:19

answered Feb 18 '21 at 07:02

Barmar

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Because I called it wrong, as should be obvious. – Barmar Feb 18 '21 at 07:19

score 1 · Answer 3 · answered Feb 18 '21 at 07:07

1

To sort a dictionary by a key "key", you can do:

sorted(dicts, key=lambda d: d["key"])

Merging this with the answer from the question you linked:

m = ["Monday", "Tuesday", ...]
print(sorted(dicts, key=lambda d: m.index(d["day"])))

answered Feb 18 '21 at 07:07

Roy Cohen

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score 0 · Answer 4 · answered Feb 18 '21 at 07:16

Here it is:

lst = [{'day' : 'Wednesday' , 'workers' : ['John' , 'Smith']} ,
       {'day' : 'Monday' , 'workers' : ['Kelly']},
       {'day' : 'Friday' , 'workers' : ['Nelly']}]

m = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]
result = sorted(lst, key= lambda x: m.index(x['day']))

print(result)
#[{'day': 'Monday', 'workers': ['Kelly']}, {'day': 'Wednesday', 'workers': ['John', 'Smith']}, {'day': 'Friday', 'workers': ['Nelly']}]

Sorting list of dictionaries in python by day of week

4 Answers4