Скачать или смотреть How to Successfully Loop Over a DataFrame and Save Each Filter to Different Excel Tabs

Learn how to loop through a pandas DataFrame and save filtered data to different sheets in an Excel file using Python!
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How to Successfully Loop Over a DataFrame and Save Each Filter to Different Excel Tabs

When working with data in Python, one of the most powerful libraries you can use is pandas. However, you might run into challenges such as saving data correctly into Excel files. Specifically, you may want to filter your DataFrame multiple times and save these filters into separate sheets within the same Excel file. Let’s explore a common problem and its solution for efficiently managing your data export.

The Problem: Overwriting Data in Excel

Imagine you've got a pandas DataFrame with various entries, and you want to create separate tabs in an Excel file for distinct names. You might think of looping through a list of names and applying a filter for each one. However, you encounter an issue: only the last tab gets saved, while the others seem to disappear!

Here’s the code you might find yourself working with:

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Why This Happens

The mistake in the above approach is that a new writer object is created in each iteration of the loop. Consequently, the Excel file gets overwritten every time, resulting in only the last filter being saved.

The Solution: Correctly Utilize the ExcelWriter

To resolve this issue, you need to move the creation of the ExcelWriter object outside the loop and close it after all the filtering and saving are complete. Here’s how to do it correctly:

Step-by-Step Implementation

Set Up Your DataFrame
Create your initial DataFrame with the necessary columns.

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Create a List of Unique Names
Define the names you want to filter by.

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Instantiate the ExcelWriter Before the Loop
Create the ExcelWriter object outside of your loop to prevent overwriting.

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Loop and Filter Data
Use a loop to filter your DataFrame using each name in the list and save them in different sheets.

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Close the Writer
Finally, ensure to close your ExcelWriter after all sheets are written.

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Final Code

Here’s the complete and corrected code for your task:

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Conclusion

By following the steps outlined above, you should now be able to loop over your DataFrame efficiently and save each filtered output to individual sheets in an Excel file without losing any data. This is a crucial skill when managing larger datasets and exporting them for analysis or sharing with others.

Remember, always create your ExcelWriter outside of your loops to avoid overwriting issues! Happy coding!