Finding duplicated values in a dictionary in Python

Question

I am trying to write a script finding duplicated values in a dictionary. My dictionary is having an integer key and a list as a value:

{5: ['13139', '3219', '3'], 6: ['14072', '3214', '3'], 7: ['13137', '3219', '3'], 8: ['13141', '3219', '3'], 9: ['13139', '3219', '3']}

Here is my code:

for key, value in dict.iteritems():
                for other_key, other_value in dict.iteritems():
                    if value == other_value and key != other_key:
                        print "We have duplicated values at key {} and key {}".format(key, other_key)

The problem is that when I run the script I got duplicated lines like this:

We have duplicated values at key 5 and key 9
We have duplicated values at key 9 and key 5

So I want to omit the second row and this script also won't show me if I have duplicated values on more than 2 keys for example if I have duplicated values at key 5, 9 and 52 it will show me:

We have duplicated values at key 5 and key 9
We have duplicated values at key 5 and key 52
We have duplicated values at key 9 and key 5
We have duplicated values at key 9 and key 52

And I want to show me that I have duplicated values at key 5, 9 and 52

I also want to show me all the keys with duplicated values so for example I can have duplication at key 5, 9 and 52 and another duplication of the values at key 40 and 65.

abc · Accepted Answer · 2018-08-21 08:46:26Z

2

You can convert your dictionary from key-> values to a new dictionary value -> keys with associated that value and obtain in such a way the duplicates.

Example:

d = {'a':[1,2],'b':[3,1],'c':[2,1,5]}

values_keys = {}

for key in d.keys():
    for value in d[key]:
        if value not in values_keys:
            values_keys[value] = [key]
        else:
            values_keys[value].append(key)

for key, value in values_keys.items():
    if len(value) > 1:
        print("key {}: We have duplicated values at keys {}".format(key,','.join(map(str, value))))

edited Aug 21, 2018 at 8:46

answered Aug 21, 2018 at 7:47

abc

12k2 gold badges30 silver badges55 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

ducminh Over a year ago

Using collections.defaultdict would yield more concise code.

Georgi Stoyanov Over a year ago

@ducminh how can I use collections.defaultdict in my case. I have integers as keys and lists as values in my dictionary. I want to find all the duplicated values and print the keys containing the duplicated values.

Georgi Stoyanov Over a year ago

@newbie I got a TypeError:

print("key {}: We have duplicated values at keys {}".format(key,','.join(value))) TypeError: sequence item 0: expected string, int found

abc Over a year ago

I tried it and works fine for both python 2.X and 3.X tio.run/…

ducminh Over a year ago

','.join(value) works only if value is a sequence of strings, while OP's keys are integers, not strings. We need to map the elements in value to strings: ','.join(map(str, value)).

|

ducminh · Accepted Answer · 2018-08-21 08:56:10Z

Both solutions provided do not completely solve the problem. To collect the duplicated values, we need to create an "inverse" dictionary, whose keys are the values of the original dictionary. As @GeorgeStoyanov pointed out that keys are integers and values are lists, we need to convert these lists to tuples to be able to use them as keys of the inverse dict.

from collections import defaultdict

d = {5: ['13139', '3219', '3'], 6: ['14072', '3214', '3'], 7: ['13137', '3219', '3'], 8: ['13141', '3219', '3'],
     9: ['13139', '3219', '3']}

val_to_keys = defaultdict(list)

for k, v in d.items():
    val_to_keys[tuple(v)].append(k)

for collected_keys in val_to_keys.values():
    if len(collected_keys) > 1:
        print(collected_keys)

Output: [9, 5]

If you are using Python 2, you might want to change items() and values() to iteritems() and itervalues().

Collectives™ on Stack Overflow

Finding duplicated values in a dictionary in Python

2 Answers 2

7 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

7 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related