[Tutor] mode?? (original) (raw)

Kent Johnson kent_johnson at skillsoft.com
Tue Jul 27 02:42:19 CEST 2004

Here is one way to do it. This will find the mode(s) of a list of any kind of items, not just numbers.

Kent

def mode(items): "Find the mode(s) of a list of items"

 # If items is empty then there is no mode
 if not items:
     return None

 # Create a dictionary that maps each item to the number of times it occurs
 # (i.e. a histogram)
 hist = {}
 for item in items:
     count = hist.get(item, 0)
     hist[item] = count + 1

 # Get the results to a list and sort by number of occurrances
 result = [ (count, item) for item, count in hist.items() ]
 result.sort()
 result.reverse()

 # The first entry has the number of times the mode occurs
 maxcount = result[0][0]

 # Find all the items that occur maxcount times
 modes = [ item for count, item in result if count == maxcount ]

 return modes

print mode([1,2,2,5,3,4,6,5]) print mode([]) print mode(['a', 2, 'b', 2, 'a', 'a'])

prints [5, 2] None ['a']

At 07:52 PM 7/26/2004 -0400, jason hochstein wrote:

I am having trouble understanding how you would get a program to output the mode of a group of numbers. I got it to do the mean and median but if there are 7 n umbers and all are different how would you get a mode. Further more if there a re 7 numbers and 2 or 3 are the same, I understand thats the mode but how do you get it to output?

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