customer2vec-data-preparation.py

orders.sort_values(by=['user_id','order_number','add_to_cart_order'], 
                   inplace=True)

orders_by_uid = orders.groupby("user_id")
                      .apply(lambda order: ' '.join(order['product_id'].tolist()))

orders_by_uid = pd.DataFrame(orders_by_uid,  
                             columns=['all_orders'])
orders_by_uid.reset_index(inplace=True)
orders_by_uid.user_id = orders_by_uid.user_id.astype(str)