INDEXING IN SERIES

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In this tutorial, we will be looking in depth about indexing in Series. We will achieve that by performing indexing operations on a Series. Furthermore, we will be using loc and iloc methods to know indexing in detail.



indexing-in-series

Performing Indexing in Series

This tutorial will discuss in detail about how to perform indexing of Series. It is important to understand that our index values don’t have to be whole numbers. We can perform indexing on strings as well. For example:

fruits = pd.Series([10,20,30,40,50], index=['apple','banana','orange','pear','peach'], name="Values")
print(fruits)

Output:

apple 10
banana 20
orange 30
pear 40
peach 50
Name: Values, dtype: int64

In order to find the index-only values, you can use the index function along with the series name and in return you will get all the index values as well as datatype of the index.

fruits.index

Output:

Index(['apple', 'banana', 'orange', 'pear', 'peach'], dtype='object')

Above, you can see the data type of the index declared as an ‘object’. If the indexes were integers then the datatype would have been int.



Is Index Value Unique?

We can also check whether the index value in a Series is unique or not by using the is_unique() method in Pandas which will return our answer in Boolean (either True or False). If all values are unique then the output will return True, if values are identical then the output will return False. For example:

fruits.index.is_unique

Output:

True

Above, we can see that we have all the unique values are our indexes, hence the output is True.

Negative Indexing in Series

You can also access the element of a Series by adding negative indexing, for example to fetch the last element of the Series, you will call ‘-1’ as your index position and see what your output is:

fruits[-1]

Output:

50

Learn more about negative indexing in python here



iloc and loc Indexing in Series

iloc and loc methods are used for indexing labels and index positions respectively. iloc method is specifically used for indexing index position and never a label, otherwise an error will pop up as:

TypeError: Cannot index by location index with a non-integer key

Whereas, loc method is used for indexing only labels, so if you have indexes as strings or strings of even numbers as ‘12’, it’s always a good practice to use loc as an index method.

Let’s have a quick look at these examples separately:

For iloc:

Fruits.iloc[1]

Output:

20

For loc:

fruits.loc['apple']

Output:

10



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