CODEWITHSUNDEEP
pythonlistpython-3.x
AnthonyWC
AnthonyWC

Reputation: 1960

Check for duplicate list/dict value inside a list

If I have a list of dictionary or a list of list where each elements are equal sized, e.g. 2 elements → [{1,2}, {3,4}, {4,6}, {1,2}] or [[1,2], [3,4], [4,6], [1,2]]

How do I check for duplicate and keep count of repeated times?

For list, something like this would work but I can't use set directly in my case.

recur1 = [[x, status.count(x)] for x in set(list1)]

Upvotes: 0

Views: 65

Answers (3)

Fuji Komalan
Fuji Komalan

Reputation: 2047

ll = [[1,2], [3,4], [4,6], [1,2]]

# Step1 Using a dictionary.

counterDict = {}
for l in ll:
  key = tuple(l) # list can not be used as a dictionary key.
  if key not in counterDict:
    counterDict[key] = 0 
  counterDict[key] += 1 
print(counterDict)  


# Step2 collections.Counter()
import collections
c = collections.Counter([ tuple(l) for l in ll])
print(c)  


# Step3 list.count()
for l in ll:
  print(l , ll.count(l))

Upvotes: 0

Ajax1234
Ajax1234

Reputation: 71451

You can use Counter from collections:

from collections import Counter

the_list = [[1,2], [3,4], [4,6], [1,2]]
new_list = map(tuple, the_list)
the_dict = Counter(new_list)

final_list = [a for a, b in the_dict.items() if b > 1]
#the number of duplicates:
print len(final_list)
#the duplicates themselves:
print final_list

if len(final_list) > 0:
   print "Duplicates exist in the list"
   print "They are: "
   for i in final_list:
       print i

else:
    print "No duplicates"

Upvotes: 0

juanpa.arrivillaga
juanpa.arrivillaga

Reputation: 95948

The easiest way is to use a Counter, but you have to convert to a hashable (i.e. immutable) type:

>>> from collections import Counter
>>> objs = [{1,2}, {3,4}, {4,6}, {1,2}]
>>> counts = Counter(objs)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/juan/anaconda3/lib/python3.5/collections/__init__.py", line 530, in __init__
    self.update(*args, **kwds)
  File "/Users/juan/anaconda3/lib/python3.5/collections/__init__.py", line 617, in update
    _count_elements(self, iterable)
TypeError: unhashable type: 'set'

So, for a set, the natural choice is a frozenset:

>>> counts = Counter(frozenset(s) for s in objs)
>>> counts
Counter({frozenset({1, 2}): 2, frozenset({4, 6}): 1, frozenset({3, 4}): 1})
>>>

This is assuming order doesn't matter, although, you can create an OrderedCounter almost trivially...

If instead you have a list of lists, a tuple would be the natural choice:

>>> objs = [[1,2], [3,4], [4,6], [1,2]]
>>> counts = Counter(tuple(l) for l in objs)
>>> counts
Counter({(1, 2): 2, (3, 4): 1, (4, 6): 1})

Upvotes: 2

Related Questions