Stupid Python tricks, #3296: sorting a dictionary by its values
Suppose you have a dictionary mydict, with key:value pairs
mydict = {'a':5, 'b':2, 'c':1, 'd':6}
You want to sort the keys by the values, maintaining the keys first in a list of tuples, so that the final list will be:
[('c',1), ('b',2), ('a',5), ('d',6)]
aaaand, the stupid Python trick involves a nested list comprehension:
sorted_list = [(k,v) for v,k in sorted(
[(v,k) for k,v in mydict.items()]
)
]
To get a reverse sorted list:
[('d',6), ('a',5),('b',2),('c',1)]
[(k,v) for v,k in sorted( [(v,k) for k,v in mydict.items()],reverse=True ) ]
Crikey. That’s a stupid python if I ever held one!
This may be a better way to do it:
sorted(mydict.items(), key = lambda (k,v): v)
You are right. It is better. But it is not stupid.
import operator
mydict = {‘a’:5, ‘b’:2, ‘c’:1, ‘d’:6}
print sorted(mydict.iteritems(), key=operator.itemgetter(1))