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Python | Pandas Index.value_counts()

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  • Difficulty Level : Basic
  • Last Updated : 23 Nov, 2021
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Python is a great language for doing data analysis, primarily because of the fantastic ecosystem of data-centric python packages. Pandas is one of those packages and makes importing and analyzing data much easier.
Pandas Index.value_counts() function returns object containing counts of unique values. The resulting object will be in descending order so that the first element is the most frequently-occurring element. Excludes NA values by default.
 

Syntax: Index.value_counts(normalize=False, sort=True, ascending=False, bins=None, dropna=True)
Parameters : 
normalize : If True then the object returned will contain the relative frequencies of the unique values. 
sort : Sort by values 
ascending : Sort in ascending order 
bins : Rather than count values, group them into half-open bins, a convenience for pd.cut, only works with numeric data 
dropna : Don’t include counts of NaN.
Returns : counts : Series 
 

Example #1: Use Index.value_counts() function to count the number of unique values in the given Index.
 

Python3




# importing pandas as pd
import pandas as pd
 
# Creating the index
idx = pd.Index(['Harry', 'Mike', 'Arther', 'Nick',
                'Harry', 'Arther'], name ='Student')
 
# Print the Index
print(idx)


Output : 

Index(['Harry', 'Mike', 'Arther', 'Nick', 'Harry', 'Arther'], dtype='object', name='Student')

Let’s find the count of all unique values in the index. 

Python3




# find the count of unique values in the index
idx.value_counts()


Output : 

Harry     2
Arther    2
Nick      1
Mike      1
Name: Student, dtype: int64

The function has returned the count of all unique values in the given index. Notice the object returned by the function contains the occurrence of the values in descending order. 
  
Example #2: Use Index.value_counts() function to find the count of all unique values in the given index.

Python3




# importing pandas as pd
import pandas as pd
 
# Creating the index
idx = pd.Index([21, 10, 30, 40, 50, 10, 50])
 
# Print the Index
print(idx)


Output : 

Int64Index([21, 10, 30, 40, 50, 10, 50], dtype='int64')

Let’s count the occurrence of all the unique values in the Index.

Python3




# for finding the count of all
# unique values in the index.
idx.value_counts()


Output : 

10    2
50    2
30    1
21    1
40    1
dtype: int64

The function has returned the count of all unique values in the index.


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