Question

How do I create a nested dictionary in python
So, I want the data be in this form..

{Category_id: {Product_id:... productInstance},{prod_id_1: this instance}}

Basically if i do something like this
lets say I want to check whether the

product_id = 5 is in category 1.

so if I do

Dict[1].has_key(5)--> be true or false..

My bad code is

fin = readFile(db)
categoryDict = defaultdict(list)
itemDict ={}
for line in fin:
    itemInstance = setItemInstances(line)

    itemDict[itemInstance._product_id] = itemInstance
    categoryDict[itemInstance._category_id].append(itemDict)




EDIT: example
dict = {1: { p_id: p_instance_1,
           p_id_2: p_ins_2}
     2:{ p_in_this_cat_id: this isntance}}

THanks

Answer 1

I think this is closer to what you want:

fin = readFile(db)
categoryDict = defaultdict(dict)     # automatically create a subdict
for line in fin:
    itemDict = {}                    # a new innermost dict for every item
    itemInstance = setItemInstances(line)
    itemDict[itemInstance._product_id] = itemInstance
    categoryDict[itemInstance._category_id] = itemDict