How to present Hierarchical Data in Pandas DataFrame in Python

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How to present Hierarchical Data in Pandas DataFrame in Python

Presenting hierarchical data in a Pandas DataFrame in Python can be a challenging task, but it’s a powerful way to represent and analyze complex data structures. In this blog, we will go over the basic concepts of hierarchical data and how to use Pandas to present it in a DataFrame.

Hierarchical data is data that has a parent-child relationship, where each parent has one or more children and each child has a single parent. In a Pandas DataFrame, hierarchical data is represented using multi-level indexing. A multi-level index is a combination of one or more columns that are used to index the rows in a DataFrame.

One way to create a multi-level index in Pandas is by using the set_index() method. This method allows you to set one or more columns as the index for a DataFrame. For example, if you have a DataFrame df with columns “City”, “Gender”, and “Age”, and you want to set the “City” and “Gender” columns as the index, you would use the following code:

df.set_index(["City", "Gender"])

 

This will create a multi-level index with the “City” and “Gender” columns, and the rows in the DataFrame will be indexed by the unique combinations of “City” and “Gender”.

You can also create a multi-level index while creating the dataframe, you can pass a list of tuples where each tuple represents the indexes of each level

pd.DataFrame({
'A': [1, 2, 3],
'B': [4, 5, 6],
'C': [7, 8, 9],
},
index=[
('a', 'x', 'p'),
('a', 'y', 'q'),
('b', 'x', 'r')
])

 

To access the rows in a DataFrame with a multi-level index, you can use the .loc property. This property allows you to select rows in a DataFrame by label. For example, if you have a DataFrame with a multi-level index and you want to select all rows where the “City” is “New York” and the “Gender” is “Female”, you would use the following code:

df.loc[("New York","Female"),:]

 

It’s also possible to select multiple levels or a single level using .loc

You can also perform operations on the dataframe with a multi-level index, for example, you can groupby on certain levels

df.groupby(level=[0,1]).sum()

 

This will group the DataFrame by the first and second level of the index, and then it will return the sum of the rest of the columns.

It’s worth noting that a multi-level index can also make it harder to perform certain operations such as sorting, filtering, and visualizing the data. Therefore, it’s important to choose the right level of granularity and use the right techniques to work with hierarchical data in a Pandas DataFrame.

 

In conclusion, representing hierarchical data in a Pandas DataFrame in Python is a powerful way to represent and analyze complex data structures. With the set_index() method, the loc property and the groupby() method, it’s easy to create and manipulate a multi-level index in a DataFrame. When working with hierarchical data, it’s important to choose the right level.

In this Learn through Codes example, you will learn: How to present Hierarchical Data in Pandas DataFrame in Python.



 

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