partition_and_save.py

import pandas as pd

# Convert customer id to partition number
members['partition'] = members['msno'].apply(id_to_hash)

# Iteration through grouped partitions
for partition, grouped in members.groupby('partition'):
    
    # Open file for appending
    with open(file_dir + f'p{partition}/members.csv', 'a') as f:
        # Write a new line and then the contents of the dataframe
        f.write('\n')
        grouped.to_csv(f, header = False, index = False)