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Get unique values from a list in Python
A list in python is a number of items placed with in [] which may or may not have same data types. It can also contain duplicates. In this article we will see how to extract only the unique values from a list.
With append()
In this approach we will first create a new empty list and then keep appending elements to this new list only if it is not already present in this new list. A for loop is used along with not in condition. It checks for the existence of the incoming element and it is appended only if it is not already present.
Example
def catch_unique(list_in):
# intilize an empty list
unq_list = []
# Check for elements
for x in list_in:
# check if exists in unq_list
if x not in unq_list:
unq_list.append(x)
# print list
for x in unq_list:
print(x)
Alist = ['Mon', 'Tue', 'Mon', 'wed', 40, 40]
print("Unique values from the list is")
catch_unique(Alist)Output
Running the above code gives us the following result −
Unique values from the list is Mon Tue wed 40
With Set
A set only contains unique values. In this approach we convert the list to a set and then convert the set back to a list which holds all the unique elements.
Example
Alist = ['Mon', 'Tue', 'Mon', 'wed', 40, 40]
A_set = set(Alist)
New_List=list(A_set)
print("Unique values from the list is")
print(New_List)Output
Running the above code gives us the following result −
Unique values from the list is [40, 'Tue', 'wed', 'Mon']
Using numpy
The numpy library has a function named unique which does the straight job of taking the list as input and giving the unique elements as a new list.
Example
import numpy as np
Alist = ['Mon', 'Tue', 'Mon', 'wed', 40, 40]
print("The unique values from list is: ")
print(np.unique(Alist))Output
Running the above code gives us the following result −
The unique values from list is: ['40' 'Mon' 'Tue' 'wed']
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