Get a List of Distinct Values in List

Get unique values in List of Lists

array = [['a','b'], ['a', 'b','c'], ['a']]
result = {x for l in array for x in l}

How to get only distinct values from a list?

This is what you needed with set():

>>> lst1 = ['A','A','A','B','C','C','D','D','D','B','B']
>>> list(set(lst1))
['A', 'B', 'D', 'C']

Another solution OrderedDict to keep the order of keys during insertion.

>>> from collections import OrderedDict
>>> list(OrderedDict.fromkeys(lst1))
['A', 'B', 'C', 'D']

In case you have liberty to use pandas then try below ones..

>>> import pandas as pd
>>> drop_dups  = pd.Series(lst1).drop_duplicates().tolist()
>>> drop_dups
['A', 'B', 'C', 'D']

In case you are looking for common values between two files:

$ cat getcomn_vals.py
#!/python/v3.6.1/bin/python3
def print_common_members(a, b):
    """
    Given two sets, print the intersection, or "No common elements".
    Remove the List construct and directly adding the elements to the set().
    Hence assigned the dataset1 & dataset2 directly to set()
    """

    print('\n'.join(s.strip('\n') for s in a & b) or "No common element")

with open('file1.txt') as file1, open('file2.txt') as file2:
    dataset1 = set(file1)
    dataset2 = set(file2)
    print_common_members(dataset1, dataset2)

Get a list of distinct values in List

Notes.Select(x => x.Author).Distinct();

This will return a sequence (IEnumerable<string>) of Author values -- one per unique value.

How to get a unique value from a list in python

Count the items, keep only those which have a count of 1:

>>> data = ['a','a','b','a']
>>> from collections import Counter
>>> [k for k,v in Counter(data).items() if v == 1]
['b']

Add only unique values to a list in python

To eliminate duplicates from a list, you can maintain an auxiliary list and check against.

myList = ['Arise', 'But', 'It', 'Juliet', 'Who', 'already', 'and', 'and', 'and', 
     'breaks', 'east', 'envious', 'fair', 'grief', 'is', 'is', 'is', 'kill', 'light', 
     'moon', 'pale', 'sick', 'soft', 'sun', 'sun', 'the', 'the', 'the', 
     'through', 'what', 'window', 'with', 'yonder']

auxiliaryList = []
for word in myList:
    if word not in auxiliaryList:
        auxiliaryList.append(word)

output:

['Arise', 'But', 'It', 'Juliet', 'Who', 'already', 'and', 'breaks', 'east', 
  'envious', 'fair', 'grief', 'is', 'kill', 'light', 'moon', 'pale', 'sick',
  'soft', 'sun', 'the', 'through', 'what', 'window', 'with', 'yonder']

This is very simple to comprehend and code is self explanatory. However, code simplicity comes on the expense of code efficiency as linear scans over a growing list makes a linear algorithm degrade to quadratic.

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If the order is not important, you could use set()

A set object is an unordered collection of distinct hashable objects.

Hashability makes an object usable as a dictionary key and a set member, because these data structures use the hash value internally.

Since the average case for membership checking in a hash-table is O(1), using a set is more efficient.

auxiliaryList = list(set(myList))

output:

['and', 'envious', 'already', 'fair', 'is', 'through', 'pale', 'yonder', 
 'what', 'sun', 'Who', 'But', 'moon', 'window', 'sick', 'east', 'breaks', 
 'grief', 'with', 'light', 'It', 'Arise', 'kill', 'the', 'soft', 'Juliet']

How to get unique values from a python list of objects

Use a set comprehension. Sets are unordered collections of unique elements, meaning that any duplicates will be removed.

cars = [...] # A list of Car objects.

models = {car.model for car in cars}

This will iterate over your list cars and add the each car.model value at most once, meaning it will be a unique collection.

How to make lists contain only distinct element in Python?

The simplest is to convert to a set then back to a list:

my_list = list(set(my_list))

One disadvantage with this is that it won't preserve the order. You may also want to consider if a set would be a better data structure to use in the first place, instead of a list.

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