python之嵌套字典 python

如何在 python 中创建嵌套字典 所以，我希望数据采用这种形式..

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

基本上如果我做这样的事情 假设我想检查

product_id = 5 is in category 1. 

如果我这样做

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

我的错误代码是

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}} 

谢谢

请您参考如下方法:

我认为这更接近你想要的:

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