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Python | Get unique values from a list

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  • Difficulty Level : Easy
  • Last Updated : 26 Jul, 2022
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Given a list, print all the unique numbers in any order.

Examples: 

Input : 10 20 10 30 40 40
Output : 10 20 30 40 
Input : 1 2 1 1 3 4 3 3 5 
Output : 1 2 3 4 5  

Method 1: Traversal of list

Using traversal, we can traverse for every element in the list and check if the element is in the unique_list already if it is not over there, then we can append it to the unique_list. This is done using one for loop and another if statement which checks if the value is in the unique list or not which is equivalent to another for a loop.  

Python




# Python program to check if two
# to get unique values from list
# using traversal
  
# function to get unique values
  
  
def unique(list1):
  
    # initialize a null list
    unique_list = []
  
    # traverse for all elements
    for x in list1:
        # check if exists in unique_list or not
        if x not in unique_list:
            unique_list.append(x)
    # print list
    for x in unique_list:
        print x,
  
  
# driver code
list1 = [10, 20, 10, 30, 40, 40]
print("the unique values from 1st list is")
unique(list1)
  
  
list2 = [1, 2, 1, 1, 3, 4, 3, 3, 5]
print("\nthe unique values from 2nd list is")
unique(list2)

Output: 

the unique values from 1st list is
10 20 30 40 
the unique values from 2nd list is
1 2 3 4 5

Python-Foundation-Course

Method 2: Using Set

Using set() property of Python, we can easily check for the unique values. Insert the values of the list in a set. Set only stores a value once even if it is inserted more than once. After inserting all the values in the set by list_set=set(list1), convert this set to a list to print it. 

Python




# Python program to check if two
# to get unique values from list
# using set
  
# function to get unique values
  
  
def unique(list1):
  
    # insert the list to the set
    list_set = set(list1)
    # convert the set to the list
    unique_list = (list(list_set))
    for x in unique_list:
        print x,
  
  
# driver code
list1 = [10, 20, 10, 30, 40, 40]
print("the unique values from 1st list is")
unique(list1)
  
  
list2 = [1, 2, 1, 1, 3, 4, 3, 3, 5]
print("\nthe unique values from 2nd list is")
unique(list2)

Output

the unique values from 1st list is
40 10 20 30 
the unique values from 2nd list is
1 2 3 4 5

Method 3: Using numpy.unique

Using Python’s import numpy, the unique elements in the array are also obtained. In the first step convert the list to x=numpy.array(list) and then use numpy.unique(x) function to get the unique values from the list. numpy.unique() returns only the unique values in the list. 

Python3




# Python program to check if two
# to get unique values from list
# using numpy.unique
import numpy as np
  
# function to get unique values
  
  
def unique(list1):
    x = np.array(list1)
    print(np.unique(x))
  
  
# driver code
list1 = [10, 20, 10, 30, 40, 40]
print("the unique values from 1st list is")
unique(list1)
  
  
list2 = [1, 2, 1, 1, 3, 4, 3, 3, 5]
print("\nthe unique values from 2nd list is")
unique(list2)

Output: 

the unique values from 1st list is
[10 20 30 40]

the unique values from 2nd list is
[1 2 3 4 5]

Method #4: Using collections.Counter()

Using python import Counter() from collections print all the keys of Counter elements or we print directly by using the “*” symbol. Below is the implementation of above approach.

Python3




# Python program to check if two
# to get unique values from list
# importing counter from collections
  
from collections import Counter
  
# Function to get unique values
  
  
def unique(list1):
  
    # Print directly by using * symbol
    print(*Counter(list1))
  
  
# driver code
list1 = [10, 20, 10, 30, 40, 40]
print("the unique values from 1st list is")
unique(list1)
  
  
list2 = [1, 2, 1, 1, 3, 4, 3, 3, 5]
print("\nthe unique values from 2nd list is")
unique(list2)

Output

the unique values from 1st list is
10 20 30 40

the unique values from 2nd list is
1 2 3 4 5

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