Looking for a fast way to build export of all possibilities (Python 2.5)

Question

I am looking for a fast way to build export.

Got three array as input data - two regular arrays and one array of dictionaries:

companies = ["company1", "company2", "company3", "company4", "company5", "company6", "company7", "company8", "company9"]
products = ["product1", "product2", "product3", "product4", "product5"]
mappings = [{"company": "company1", "product": "product1"},
            {"company": "company1", "product": "product2"},
            {"company": "company1", "product": "product3"},
            {"company": "company3", "product": "product6"},
            {"company": "company3", "product": "product9"},
            {"company": "company4", "product": "product2"}
            ]

'mappings' array may contain from 0 to 20,000 records. I need a fast way to build the following export:

mappings_export = [{"company": "company1", "product": "product1", "is_mapped": 1},
                   {"company": "company1", "product": "product2", "is_mapped": 1},
                   {"company": "company1", "product": "product3", "is_mapped": 1},
                   {"company": "company1", "product": "product4", "is_mapped": 0},
                   {"company": "company1", "product": "product5", "is_mapped": 0},
                   {"company": "company1", "product": "product6", "is_mapped": 1}
                   ]

I tried using this way, but it is very slow:

mappings_export = []
for company in companies:
    for product in products:
        found = filter(lambda x: x["product"] == product and x["company"] == company, mappings)
        if len(found) > 0:
            mapped = 1
        else:
            mapped = 0
        mappings_export.append({"company": company,
                                "product": product,
                                "mapped": mapped})

Thank you!

Answer 1

This is python3 (sorry, i don't have a python 2 compiler so i can't check), but is very basic and maybe you can adopt it. It is faster because I create a set out of mappings to avoid running filter all the time.

company_product = set([])

for m in mappings:
    company_product.add((m["company"],m["product"]))

mappings_export = []
for c in companies:
    for p in products:
        mappings_export.append({"company": c,
                                "product": p,
                                "mapped": 1 if (c,p) in company_product else 0})