Introduction
In this lab, we will learn how to use the combine_first() method in the Pandas DataFrame. This method allows us to combine two DataFrame objects by filling null values in one DataFrame with non-null values from another DataFrame. It can be useful when we have missing data in one DataFrame and want to fill it with data from another DataFrame.
VM Tips
After the VM startup is done, click the top left corner to switch to the Notebook tab to access Jupyter Notebook for practice.
Sometimes, you may need to wait a few seconds for Jupyter Notebook to finish loading. The validation of operations cannot be automated because of limitations in Jupyter Notebook.
If you face issues during learning, feel free to ask Labby. Provide feedback after the session, and we will promptly resolve the problem for you.
Import the necessary libraries
import pandas as pd
Create two DataFrames with missing values
df1 = pd.DataFrame({'A': [None, 0], 'B': [None, 4]})
df2 = pd.DataFrame({'A': [1, 1], 'B': [3, 3]})
Combine the DataFrames using the combine_first() method
combined_df = df1.combine_first(df2)
Print the combined DataFrame
print(combined_df)
Add a new row to one of the DataFrames
df2.loc[2] = [2, 2]
Combine the DataFrames again
combined_df = df1.combine_first(df2)
Print the combined DataFrame again
print(combined_df)
Combine DataFrames with None values
df1 = pd.DataFrame({'A': [None, 0], 'B': [None, 4]})
df2 = pd.DataFrame({'A': [None, 1], 'B': [None, 3]})
combined_df = df1.combine_first(df2)
print(combined_df)
Combine DataFrames with different indexes
df1 = pd.DataFrame({'A': [None, 0], 'B': [4, None]})
df2 = pd.DataFrame({'B': [3, 3], 'C': [1, 1]}, index=[1, 2])
combined_df = df1.combine_first(df2)
print(combined_df)
Summary
In this lab, we learned how to use the combine_first() method in the Pandas DataFrame. We saw that this method allows us to fill null values in one DataFrame with non-null values from another DataFrame. We also saw how it can handle cases where both DataFrames have null values or when the DataFrames have different indexes. The combine_first() method is a useful tool for combining and filling missing data in DataFrames.