total_buys.py

import requests
import datetime

from functools import reduce
from operator import add

def main():
    max_pages = 3
    i = 0
    
    running_total = 0
    
    while i < max_pages:
        request_string = "https://api.guildwars2.com/v2/commerce/listings?page={}&page_size=200".format(i)
        print("Requesting page {} of {}".format(i, max_pages))
        
        result = requests.get(request_string)       
        max_pages = int(result.headers['X-Page-Total'])
        item_array = result.json()
        
        running_total += reduce(add,
                                map(lambda x: reduce(add, 
                                                     map(lambda y: y["listings"] * y["unit_price"] * y["quantity"], x["buys"]),
                                                     0), 
                                    item_array),
                               0)                

        print(running_total)
        
        i += 1
       
    print("Total there is {} on the TP".format(running_total))


if __name__ == "__main__":
    main()