Get the key corresponding to the minimum value within a dictionary

For multiple keys which have equal lowest value, you can use a list comprehension:

d = {320:1, 321:0, 322:3, 323:0}

minval = min(d.values())
res = [k for k, v in d.items() if v==minval]

[321, 323]

An equivalent functional version:

res = list(filter(lambda x: d[x]==minval, d))

min(zip(d.values(), d.keys()))[1]

Use the zip function to create an iterator of tuples containing values and keys. Then wrap it with a min function which takes the minimum based on the first key. This returns a tuple containing (value, key) pair. The index of [1] is used to get the corresponding key.

I compared how the following three options perform:

    import random, datetime

myDict = {}
for i in range( 10000000 ):
    myDict[ i ] = random.randint( 0, 10000000 )



# OPTION 1

start = datetime.datetime.now()

sorted = []
for i in myDict:
    sorted.append( ( i, myDict[ i ] ) )
sorted.sort( key = lambda x: x[1] )
print( sorted[0][0] )

end = datetime.datetime.now()
print( end - start )



# OPTION 2

start = datetime.datetime.now()

myDict_values = list( myDict.values() )
myDict_keys = list( myDict.keys() )
min_value = min( myDict_values )
print( myDict_keys[ myDict_values.index( min_value ) ] )

end = datetime.datetime.now()
print( end - start )



# OPTION 3

start = datetime.datetime.now()

print( min( myDict, key=myDict.get ) )

end = datetime.datetime.now()
print( end - start )

Sample output:

#option 1
236230
0:00:14.136808

#option 2
236230
0:00:00.458026

#option 3
236230
0:00:00.824048

Or __getitem__:

>>> d = {320: 1, 321: 0, 322: 3}
>>> min(d, key=d.__getitem__)
321

To create an orderable class you have to override six special functions, so that it would be called by the min() function.

These methods are__lt__ , __le__, __gt__, __ge__, __eq__ , __ne__ in order they are less than, less than or equal, greater than, greater than or equal, equal, not equal.

For example, you should implement __lt__ as follows:

def __lt__(self, other):
  return self.comparable_value < other.comparable_value

Then you can use the min function as follows:

minValue = min(yourList, key=(lambda k: yourList[k]))

This worked for me.