TypeError: string indices must be integers

[JonWayn]

given the code snippet:

i = 0

for key, value in quiz.items():
    i += 1
    print(f"Question {str(i)} : {key['question']}")

Line 5 fails with the error code,

Error:
TypeError: string indices must be integers

The variable named 'i' is clearly an integer. Can someone explain why it fails with this error?

full code:

quiz = {
    "question1": {
        "question": "What is the capital of France?",
        "answer": "Paris"
    },
    "question2": {
        "question": "What is the capital of Germany?",
        "answer": "Berlin"
    },
    "question3": {
        "question": "What is the capital of Italy?",
        "answer": "Rome"
    },
    "question4": {
        "question": "What is the capital of England?",
        "answer": "London"
    },
    "question5": {
         "question": "What is the capital of Norway?",
        "answer": "Oslo"
    },
    "question6": {
        "question": "What is the capital of Switzerland?",
        "answer": "Bern"
    },
    "question7": {
        "question": "What is the capital of Austria?",
        "answer": "Vienna"
    },
    "question8": {
        "question": "What is the capital of Spain?",
        "answer": "Madrid"
    },
    "question9": {
        "question": "What is the capital of Portugal?",
        "answer": "Lisbon"
    },
    "question10": {
        "question": "What is the capital of Belgium?",
        "answer": "Brussels"
    },
    "question11": {
        "question": "What is the capital of Sweden?",
        "answer": "Stockholm"
    },
    "question12": {
        "question": "What is the capital of Denmark?",
        "answer": "Copenhagen"
    },
    "question6": {
        "question": "What is the capital of Holland?",
        "answer": "Amsterdam"
    },
}

score = 0
i = 0

for key, value in quiz.items():
    i += 1
    print(f"Question {str(i)} : {value['question']}")
    answer = input("Answer? ")

    if answer.lower() == value['answer'].lower():
        score += 1
        print('Correct!')
    else:
        print("Incorrect :{")
        print("The correct answer is: " + value['answer'])

    print(f"Your score is {score}")

Error:
TypeError: string indices must be integers

I did get it resolved with the help of another reply but thank you for pointing me to the proper usage of the interface. It's pretty awesome