Database management in csv format

[scidam]

Take a look at Pandas. Using Pandas your pseudo-code would be as follows:

import pandas as pd
data = pd.read_csv('your_source_file_name')

for g, d in data.groupby('Item').groups.items():
    data.loc[d].to_csv("{}".format(str(g)))

I didn't test the code above, probably you will need to slightly modify it.