Reading and writing multiple files

When working on actual data projects, there are cases where data is split into multiple files in a directory. Dealing with each file one by one can be a pain and may distract you from working on other critical components of your project.

In this recipe, we’ll cover reading multiple files into a single DataFrame or into multiple DataFrames, as well as writing a DataFrame to multiple files.

How to do it...

Here are some ways to work with multiple files:

1. Write a DataFrame to multiple CSV files:
   1. Create a DataFrame:

   data = {'Letter': ['A','B','C'], 'Value': [1,2,3]}
   df = pl.DataFrame(data)

   2. Split it into multiple DataFrames:

   dfs = df.group_by(['Letter'])
   print(dfs)

   The preceding code will return the following output:

   >> <polars.dataframe.group_by.GroupBy object at 0x154373390>

   3. Write them to CSV files:

   for name, df in dfs:
       df.write_csv(f'...