Comparing nested dictionaries into general dictionary

Question

I would like to compare multiple nested dictionaries inside a larger dictionary. Suppose we have the following dictionary:

pricesDict = { "supermarket_1": {"apples": 1, "bananas": 2, "melons": 3},
               "supermarket_2": {"apples": 1.5, "bananas": 2, "melons": 3},
               "supermarket_3": {"apples": 1, "bananas": 2, "melons": 3},
               "supermarket_4": {"apples": 1, "bananas": 2.7, "melons": 3}}

I have a pricesDict that contains the prices of some products (more than 3 as shown above) in different supermarkets (more than 4 as shown above).

I want to go through it to compare the nested supermarkets with one another (e.g supermarket_1 with supermarket_2, supermarket_3 and supermarket_4, supermarket_2 with supermarket_3 and supermarket_4 and so on) to find out which one has the lowest prices.

If the programme spots a difference between the price of a specific product in two supermarkets it should print a message to inform us that there is a difference on the prices.

The output should be something like the following:

There is a price difference between supermarket_1: 1 and supermarket_2: 1.5 in apples
There is a price difference between supermarket_1: 2 and supermarket_4: 2.7 in bananas
There is a price difference between supermarket_2: 1.5 and supermarket_3: 1 in apples
There is a price difference between supermarket_2: 1.5 and supermarket_4: 1 in apples
There is a price difference between supermarket_2: 2 and supermarket_4: 2.7 in bananas
There is a price difference between supermarket_3: 2 and supermarket_4: 2.7 in bananas

Thanks!

Asked By: Marios Antakis

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Source

Answer 1

You can do it with itertools.combinations and a nested loop:

from itertools import combinations

for first_market, second_market in combinations(pricesDict, 2):
    for produce in ["apples", "bananas", "melons"]:
        first_price = pricesDict[first_market][produce]
        second_price = pricesDict[second_market][produce]
        
        if first_price != second_price:
            print(
                  f"There is a price difference between {first_market}: {first_price} " +
                  f"and {second_market}: {second_price} in {produce}"
                 )

this prints:

There is a price difference between supermarket_1: 1 and supermarket_2: 1.5 in apples
There is a price difference between supermarket_1: 2 and supermarket_4: 2.7 in bananas
There is a price difference between supermarket_2: 1.5 and supermarket_3: 1 in apples
There is a price difference between supermarket_2: 1.5 and supermarket_4: 1 in apples
There is a price difference between supermarket_2: 2 and supermarket_4: 2.7 in bananas
There is a price difference between supermarket_3: 2 and supermarket_4: 2.7 in bananas

Answered By: hhimko

Answer 2

Adding to hhmiko’s answer, we can create the list of all the products within the code like this assuming every nested supermarket dictionary contains the same keys as all other nested supermarket dictionaries.

supermarkets = list(pricesDict.keys())
items = list(pricesDict[supermarkets[0]].keys())

and substitute the items list in line 4 of her answer

Answered By: EliteGamerSiddhu

Comparing nested dictionaries into general dictionary

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