Agfdhyk

I’m new to Python 3 and have been experimenting with Dictionaries but I’m having problems testing for a specific key and retrieving its related values from nested dictionaries.

I want a user defined input to be checked against nested dictionaries and if the user input is found I then want to collect the details for that item and add it to another dictionary.

E.g.

basketDict = {}

shopDict = {"Fruit": {"Apple": "2", "Banana": "3"},

             "Vegetables": {"Lettuce": "5", "Potato": "7"}}

userQuery = input("What food do you want to check for? ")

userQuery = "Apple"

Desired result:

basketDict = {"Fruit": {"Apple": "2"}}

I've attempted to use dictionary comprehension to form a new dictionary of only food items (Apple, Banana, Lettuce etc.) but keep running into issues when trying to collect the related category ("Fruit"/"Vegetable" and quantity information from the nested dictionaries.

Here's my (broken) code:

basketDict = {}

shopDict = {"Fruit": {"Apple": "2", "Banana": "3"},

             "Vegetables": {"Lettuce": "5", "Potato": "7"}}

shopCheck = 



userQuery = input("What food do you want to check for? ")

for category, food in shopDict.items():

    for each in food:

        shopCheck.append(each)



    if userQuery not in shopCheck:

        print("That's not available.")

    else:

        print(userQuery + " added to basket. ")

        basketDict[category] = [food]



print(basketDict)

This code is enough for your requirements:

for category, food in shopDict.items():

    if userQuery in food:

        basketDict[category] = {userQuery: food[userQuery]}

But if you want to add new items to the basket, you should update it properly:

for category, food in shopDict.items():

    if userQuery in food:

        basketDict.update(

            {category: {**basketDict.get(category, {}),

                        **{userQuery: food[userQuery]}}}

        )

You want to merge the actual dictionary of the category (the basket's actual content) with the selected item's key-value.
Generally in python3 if you have 2 dictionaries this is the way to merge them into one:

d1 = {"one": 1, "two": 2}

d2 = {"three": 3}

merged = {**d1, **d2}  # {'one': 1, 'two': 2, 'three': 3}

Because ** is used to unpack the dictionary.

Good way to understand it is if you have a function definition with some arguments, then you can call the function with a dictionary that has the argument names as keys. But you have to unpack it, otherwise you would pass the dictionary as the parameter, and not its values.

d = {"one": 1, "two": 2}

def example(one, two):

    pass

example(d) would throw a TypeError, because it's missing the second positional argument, but example(**d) would work fine

Probably there's a simpler way to do this, but I just fixed your code.
When I run your code, everything inside shopDict was going to basketDict. This is because you wasn't cleaning your shopCheck variable at each for iteration.
And there was a second mistake when adding the elements to basketDict. You need to add only the food element that match the userQuery. Here's the full fixed code:

basketDict = {}

shopDict = {"Fruit": {"Apple": "2", "Banana": "3"},

            "Vegetables": {"Lettuce": "5", "Potato": "7"}}



userQuery = input("What food do you want to check for? ")

for category, food in shopDict.items():

    shopCheck = 

    for each in food:

        shopCheck.append(each)



    if userQuery not in shopCheck:

        print("That's not available.")

    else:

        print(userQuery + " added to basket. ")

        basketDict[category] = {userQuery:food[userQuery]}



print(basketDict)

I'd start by creating a dictionary containing all the items you can buy, whether they're fruit or vegetables. Then I'd simply check if the required item is on that dictionary:

basketDict = {}

shopDict = {"Fruit": {"Apple": "2", "Banana": "3"},

             "Vegetables": {"Lettuce": "5", "Potato": "7"}}

allVals = {}



for k, subDict in shopDict.items():

    for k1, val in subDict.items():

        allVals[k1] = val





userQuery = input("What food do you want to check for? ")

if userQuery not in allVals.keys():

    print("That's not available.")

else:

    print(userQuery + " added to basket. ")

    basketDict[userQuery] = allVals[userQuery]



print(basketDict)