I have to sort my list of strings according to the months name:
my_list = ['apple_april', 'banana_july', 'carrot_december', 'dog_january']
I have to sort by january, february, martch, .....
My trial:
months = [m.split('_')[1] for m in my_list]
ans = [x for (y,x) in sorted(zip(months,my_list))]
But no success, how would you do it?
The expected answers is:
['dog_january', 'apple_april', 'banana_july', 'carrot_december']
list.sort, sorted accept optional key parameter. Pass a key function that returns corresponding number to monthes.
>>> import calendar
>>>
>>> months = {calendar.month_name[i].lower(): i for i in range(1, 12+1)}
>>> my_list = ['apple_april', 'banana_july', 'carrot_december', 'dog_january']
>>> sorted(my_list, key=lambda x: months[x.split('_')[1]])
['dog_january', 'apple_april', 'banana_july', 'carrot_december']
months is mapping between month names and numbers using calendar.month_name:
>>> months
{'april': 4, 'november': 11, 'june': 6, 'august': 8, 'december': 12, 'october': 10,
'july': 7, 'march': 3, 'september':9, 'may': 5, 'january': 1, 'february': 2}
You could make a dictionary of months and their corresponding position in the calendar:
months = {'january': 1,
'april': 4,
'july': 7,
'december': 12}
And then sort the list by looking up the month in the dictionary. First split each element of the list on the underscore (which gives a list such as ['dog', 'january']) and then use months.get to look up the last element of this list in the dictionary:
>>> sorted(my_list, key=lambda x: months.get(x.split('_')[-1]))
['dog_january', 'apple_april', 'banana_july', 'carrot_december']
Edit:
A lazier way if you have dateutil installed...
>>> import dateutil
>>> sorted(my_list, key=lambda x: dateutil.parser.parse(x.split('_')[-1]))
['dog_january', 'apple_april', 'banana_july', 'carrot_december']
No need for a dictionary! dateutil.parser.parse parses the month string to a datetime object.
dateutil (+1)dateutil one should use this so that's good to know. I was looking up to see if strptime can accept wildcard characters but it turns out you need dateutil for that>>> from datetime import datetime
>>> my_list = ['apple_april', 'banana_july', 'carrot_december', 'dog_january']
>>> sorted(my_list, key=lambda x: datetime.strptime(x.split('_')[1], '%B'))
['dog_january', 'apple_april', 'banana_july', 'carrot_december']
You can sort your list based on calendar.month_name or calendar.month_abbr :
>>> import calendar
>>> m=list(calendar.month_abbr)
>>> l=[(i,x) for x in my_list for i,j in enumerate(m) if j==x.split('_')[1][:3]]
>>> [i[1] for i in sorted(l,key= lambda x: x[0])]
['dog_january', 'apple_april', 'banana_july', 'carrot_december']
