Using the python list sort method combined with lambda opens up a some nice sorting options.
Sorting by Day of Week
Lets say you have a list of dictionaries where one of the dictionary keys a string specifying a day of the week, such as ‘Monday’.
Since you can’t sort alphabetically, you must define a custom sort using a list and lambda as follows:
schedule = [ {'dayofweek' : 'Wednesday', 'task' : 'go to work' },
{'dayofweek' : 'Friday', 'task' : 'go to beach' },
{'dayofweek' : 'Friday', 'task' : 'day off' },
{'dayofweek' : 'Monday', 'task' : 'meeting with client' } ]
# define a dictionary that will assign each weekday a sort order
convert = {'Monday' : 0, 'Tuesday' : 1, 'Wednesday' : 2, 'Thursday' : 3, 'Friday' : 4, 'Saturday' : 5, 'Sunday' : 6}
# use lambda to define a comparison function for sort to use when comparing two items
schedule.sort (lambda x, y : cmp (convert[x['dayofweek']], convert[y['dayofweek']]))Sorting with a Secondary Key
Using the schedule list above, if we also want to sort by a secondary key task, the lambda function gets a little more complex:
schedule.sort (lambda x, y : cmp((convert[x['dayofweek']], x['task']), (convert[y['dayofweek']], y['task'])))