How to list unique values in a Pandas DataFrame?

How to list unique values in a Pandas DataFrame?

How to list unique values in a Pandas DataFrame?

This recipe helps you list unique values in a Pandas DataFrame


Recipe Objective

We can easily view the dataframe and sometimes we find that few of the values have been repeated many times in different rows. So if we need to find unique values or categories in the feature then what to do ?

So this is the recipe on How we can make a list of unique values in a Pandas DataFrame.

Step 1 - Import the library

import pandas as pd

We have only imported pandas which is required for this.

Step 2 - Setting up the Data

We have created a dictionary with columns 'Name', 'Year' and 'Episodes' and passed this in pd.DataFrame to create a DataFrame with index. data = {'name': ['Sheldon', 'Penny', 'Amy', 'Penny', 'Raj', 'Sheldon'], 'year': [2012, 2012, 2013, 2014, 2014,2012 ], 'episodes': [42, 24, 31, 29, 37, 40]} df = pd.DataFrame(data, index = ['a', 'b', 'c', 'd', 'e','f']) print(df)

Step 3 - Finding Unique Values and Printing it

We can find unique values by unique function in two formats:

  • series.unique() : In this we have to add the unique function after the series(column) in which we want to find the unique values.
  • pd.unique() : In this we have to pass the series as a parameter to find the unique values.
We have used both functions for better understanding. print( print(pd.unique(df['year'])) Output of the dataset comes as

      name  year  episodes
a  Sheldon  2012        42
b    Penny  2012        24
c      Amy  2013        31
d    Penny  2014        29
e      Raj  2014        37
f  Sheldon  2012        40

['Sheldon' 'Penny' 'Amy' 'Raj']

[2012 2013 2014]

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