How to Unnest a Pandas DataFrame Column into Multiple Rows?

How to Unnest a Column into Multiple Rows in a Pandas DataFrame

Problem:

You have a DataFrame where one column contains a list of values, and you want to separate each list element into its own row.

Solution:

There are several methods to unnest (or explode) a column in a Pandas DataFrame:

Method 1: Using explode (Pandas >= 0.25)

If you have a single column to unnest, the explode function is the simplest solution:

Method 2: Using apply and pd.Series

This method is straightforward but not recommended for performance reasons:

Method 3: Using repeat and DataFrame Constructor

Create a new DataFrame with the repeated values in the unnested column:

Method 4: Using reindex or loc

Create a new DataFrame with the unnested values and use reindex or loc to align it with the original:

Method 5: Using collections.ChainMap (when list contains unique values)

Method 6: Using Numpy for High Performance

This method is more efficient than the previous ones:

Method 7: Using itertools.cycle and itertools.chain

Pure Python solution for fun:

Generalizing to Multiple Columns:

The following function allows you to unnest multiple columns in a DataFrame:

Column-wise Unnesting:

If you need to unnest a column horizontally, use the add_prefix method of the DataFrame constructor:

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