[Tutor] mode??

[Kent Johnson]

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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