Dictionary sort by numer of days in month( in keys) in python

Question

I am trying to sort dictionary by number of days in month. (30,31 and 28). i have tried to achieve this by calendar module and datetime module but did not get the desired output. Any suggestion !!

product_sell= {'November':680,'August':678,'October':857,'January': 125,'April':989,'February': 300, 'September':120,'March':259,'December':899,'June':368, 'May':31,'July':968}

expected output (sort(keys) by number of months in days jan,march...=31, feb=28, april,june..=30 )

product_sell= {'January': 125, 'March':259, 'May':31, 'July':968, 'August':678,  'October':857, 'December':899, 'April':989, 'June':368, 'September':120, 'November':680, 'February': 300}

Have you tried `sorted`? Also see https://stackoverflow.com/questions/39980323/are-dictionaries-ordered-in-python-3-6?rq=1, and please only tag the version of Python you are using. — meowgoesthedog, Mar 21 '19 at 10:16
Dictionaries should be considered unordered even if they remain in insertion order in newer Python versions. Ordered data is better handled in lists. — Klaus D., Mar 21 '19 at 10:19

score 1 · Answer 1 · answered Mar 21 '19 at 10:26

You can't sort dictionaries because it is orderless. You can use ordereddict to achieve this.

from collections import OrderedDict

product_sell= {'November':680,'August':678,'October':857,'January': 125,'April':989,'February': 300, 'September':120,'March':259,'December':899,'June':368, 'May':31,'July':968}
months = ['January','February','March','April','May','June','July','August','September','October','November','December']

OrderedDict(sorted(product_sell.items(),key =lambda x:months.index(x[0])))

Output:

OrderedDict([('January', 125),
         ('February', 300),
         ('March', 259),
         ('April', 989),
         ('May', 31),
         ('June', 368),
         ('July', 968),
         ('August', 678),
         ('September', 120),
         ('October', 857),
         ('November', 680),
         ('December', 899)])

score 0 · Answer 2 · answered Mar 21 '19 at 19:38

You don't need to create a new (ordered) dictionary if you just want to consume (print, write to a file, ...) the data. Just output a list of items (month, count).

>>> product_sell= {'November':680,'August':678,'October':857,'January': 125,'April':989,'February': 300, 'September':120,'March':259,'December':899,'June':368, 'May':31,'July':968}

First, you can buld a sort key by month:

>>> import calendar
>>> key_by_month = dict(zip(calendar.month_name[1:], [(-calendar.monthrange(2019,i)[1], i) for i in range(1,13)]))
>>> key_by_month
{'January': (-31, 1), 'February': (-28, 2), 'March': (-31, 3), 'April': (-30, 4), 'May': (-31, 5), 'June': (-30, 6), 'July': (-31, 7), 'August': (-31, 8), 'September': (-30, 9), 'October': (-31, 10), 'November': (-30, 11), 'December': (-31, 12)}

Months will be sorted by number of days (descending, hence the minus sign) and then by their natural order.

Second, use sorted and find the key by the month name:

>>> sorted(product_sell.items(), key=lambda m_c: key_by_month[m_c[0]])
[('January', 125), ('March', 259), ('May', 31), ('July', 968), ('August', 678), ('October', 857), ('December', 899), ('April', 989), ('June', 368), ('September', 120), ('November', 680), ('February', 300)]

Note: If you can, avoid using month names as keys, because they are subject to variations: "january" vs "January", foreign languages, ...

Dictionary sort by numer of days in month( in keys) in python

2 Answers2