Pandas.errors.indexingerror: unalignable boolean series provided as indexer (index of the boolean series and of the indexed object do not match).

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pandas.errors.IndexingError: unalignable boolean series provided as indexer

This error occurs when you try to index a pandas DataFrame or Series using a boolean series as the indexer, but the indexes of the boolean series and the DataFrame/Series do not match.

To understand this error in detail, let’s consider an example. 

        import pandas as pd

        # Create a DataFrame
        df = pd.DataFrame({'col1': [1, 2, 3, 4], 'col2': [5, 6, 7, 8]})

        # Create a boolean series
        bool_series = pd.Series([True, False, True])

        # Try to index the DataFrame using the boolean series
        result = df[bool_series]

        # This will raise the IndexingError

In the above example, we are trying to index the DataFrame df using the boolean series bool_series. However, the lengths of the two series do not match, and hence we get the IndexingError.

To fix this error, we need to ensure that the lengths of the boolean series and the DataFrame/Series are the same. This can be done by either adjusting the length of the boolean series or aligning the indexes of the boolean series and the DataFrame/Series.

Here are two possible solutions: 

        # Solution 1: Adjusting the length of the boolean series
        bool_series = pd.Series([True, False, True, False])
        result = df[bool_series]
        # The boolean series now has the same length as the DataFrame

        # Solution 2: Aligning the indexes of the boolean series and the DataFrame
        bool_series.index = df.index
        result = df[bool_series]
        # The indexes are now aligned and the operation is successful

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