Can Pandas\' `to_csv()` Function Append Data to an Existing CSV File?

Adding Pandas Data to an Existing CSV File

When working with data manipulation, it is often necessary to update or append data to existing files. Pandas, a powerful data analysis library for Python, provides a convenient method to add a DataFrame to an existing CSV file.

Query:

Is it feasible to use the pandas to_csv() function to extend an existing CSV file, assuming the file possesses the same structural format as the data being loaded?

Answer:

Absolutely! The to_csv() function allows for the specification of a Python write mode. To append data, the mode should be set to 'a'.

Implementation:

To append a DataFrame to an existing CSV file, simply utilize the following code:

df.to_csv('my_csv.csv', mode='a', header=False)

By default, the mode is set to 'w', which overwrites the CSV file.

Ensuring Header Printing:

In cases where the initial file may be absent, it is advisable to guarantee that the header is printed during the initial write. This can be achieved with the following variation:

output_path='my_csv.csv'
df.to_csv(output_path, mode='a', header=not os.path.exists(output_path))

This extended variation ensures that the header is printed only upon the first write, effectively handling both existing and non-existent files.

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