How can I get the keys from a nested dictionary?

问题

I have a list within a dictionary within a dictionary:

{FirmA:{ProductA:[Color1,Color2,Color3]}}

I want to build a list of keys from the First Firm dictionary level.

Then, I need to access the second level Product dictionary based on a Firm Key.

Finally, I will need to access the Colors list based on the Product key from Dictionary level 2 (Products).

I tried to get the level 1 keys for Firms:

[i for i in dict.keys()]

Returns

ValueError: Too many values to unpack

This is a fairly large data set.

I have not been able to get to the 2nd level dictionary yet.

回答1:

Something like this should get you started:

def get_products_for_firm(d, firm):
    firm_letter = firm[-1]
    product_prefix = "Product"
    product_key = "%s%s" % (product_prefix, firm_letter)
    return d[firm][product_key]


d = {
    "FirmA": {
        "ProductA": ["Color1", "Color2", "Color3"]
    },
    "FirmB": {
        "ProductB": ["Color4", "Color5", "Color6"]
    }
}

firm_keys = d.keys()
print "The firm keys are %s: " % (firm_keys)

for firm_key in firm_keys:
    print "The products for %s are: %s" % (firm_key,
                                           get_products_for_firm(d, firm_key))

Output:

The firm keys are ['FirmA', 'FirmB']:
The products for FirmA are: ['Color1', 'Color2', 'Color3']
The products for FirmB are: ['Color4', 'Color5', 'Color6']

回答2:

What about that:

d = {'foo':{'bar':42}}

# you can do much like for nested list, like so:
print(d['foo'])
print(d['foo']['bar'])

# or you can iterate:
for k,v in d.items():
    print(k,v)

    # if the value is also a dictionary, iterate on it again:
    try:
        for k2, v2 in v.items():
            if isinstance(v2, list):
                for el in v2:
                    print el
    except:
        pass

EDIT: actually if it's a large dataset, and you'll have few values below the first pass actually a dictionary, it may be faster to do an instance check as well (isinstance(v, dict)), since catching is expensive. Depends on the details....

来源：https://stackoverflow.com/questions/57211388/how-can-i-get-the-keys-from-a-nested-dictionary

标签

python

python-2.7

dictionary

nested