Find Duplicate numbers in list

[LarryAdgate]

If anyone can help me with this I really would appricate it. I'm a novice

My task is to create a script a that examines a list of numbers (for example, 2, 8, 64, 16, 32 4, 16, 😎 to determine whether it contains duplicates. The script should print a meaningful result, such as "The list provided contains duplicate values" or "The list provided does not contain duplicate values."

Thanks,
Larry

[JasonScheirer]

import collections

def has_duplicates(list_of_values):
    value_dict = collections.defaultdict(int)
    for item in list_of_values:
        value_dict[item] += 1
    return any(val > 1 for val in value_dict.itervalues())

if has_duplicates(my_list):
    print "The list provided contains duplicate values"
else:
    print "The list provided does not contain duplicate values."

[Anonymous User]

Something like this should do the trick:

def FindDuplicates(in_list):
    unique = set(in_list)
    for each in unique:
        count = in_list.count(each)
        if count > 1:
            print 'There are duplicates in this list'
            return True
    print 'There are no duplicates in this list'
    return False

if __name__ == '__main__':

    # test it
    a = [8, 64, 16, 32, 4, 24]
    b = [2,2,3,6,78,65,4,4,5]

    FindDuplicates(a)
    FindDuplicates(b)
 

This printed:
IDLE 2.6.5      ==== No Subprocess ====
>>>
There are no duplicates in this list
There are duplicates in this list
>>>


Ahh looks like Jason beat me to it...both should work just fine.

[NeilAyres]

Larry,

I often do this using a dictionary and a search cursor like:

Cur = arcpy.da.SearchCursor(InFc, ["Field"]) # where Field is the column to count duplicates
FDict = {}
for r in Cur:
    f = r[0]
    if f in FDict:
        FDict += 1
    else:
        FDict = 1

del Cur

The dictionary FDict will contain the keys of all the possible values of Field and a count of how many there are.
Cheers,
Neil

[DouglasSands]

Something like this should do the trick:

def FindDuplicates(in_list):
    unique = set(in_list)
    for each in unique:
        count = in_list.count(each)
        if count > 1:
            print 'There are duplicates in this list'
            return True
    print 'There are no duplicates in this list'
    return False

Find duplicates can be much simpler if you already have the list:

def FindDuplicates(in_list):
    unique = set(in_list)
    if len(unique) == len(in_list):
        print('There are no duplicates in this list')
        return False
    else:
        print('There are duplicates in this list')
        return True


This way, you don't have to loop over the list.

[Anonymous User]

Touché...Definitely over-analyzed that one.  Easier is better.

[DanPatterson_Retired]

try "sets"

>>> a = ( 2, 8, 64, 16, 32, 4, 16, 8)
>>> b = set(a)
>>> if len(b) < len(a):
...  print "contains duplicates"
... else:
...  print "no duplicates found:"
>>> 
contains duplicates

ooops missed Doug's example

[LarryAdgate]

If anyone can help me with this I really would appricate it. I'm a novice

My task is to create a script a that examines a list of numbers (for example, 2, 8, 64, 16, 32 4, 16, 😎 to determine whether it contains duplicates. The script should print a meaningful result, such as "The list provided contains duplicate values" or "The list provided does not contain duplicate values."

Thanks,
Larry

To those that responded to my cries for help, a world of thanks. With this much help available, learning python is going to be much easer-Larry

[MikeMacRae]

Use the 'set' and 'len'. 'len' with give you a count of the values in your list. 'set' will filter out any duplicates in your list and then use len to count the list again and compare it to your original count:

list = ( 2, 8, 64, 16, 32, 4, 16, 8)

if len(list) <> len(set)list):
     print "The list provided contains duplicate values"

[RebeccaStrauch__GISP]

I didn't know about "set" before, so nice post.  I saw it because this popped up in my geonet email, but notices a syntax error above, and then expanded for a non-dupe list.  fwiw.

list = ( 2, 8, 64, 16, 32, 4, 16, 8)

if len(list) <> len(set(list)):
     print("the list provided contains duplicate values")
else:
     print("no dupes")
     
list = (1, 2, 3, 4, 5)

if len(list) <> len(set(list)):
     print("the list provided contains duplicate values")
else:
     print("no dupes")‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

edit: ....oops...I missed Doug's and Dan's examples.  shows you what happens when you go to the bottom of the geonet comments first.