CT Week 8

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Dictionary with List Values

A dictionary with list values is a dictionary where each key maps to a list of values. This is useful when you need to associate multiple values with a single key.

Examples of Dictionary with List Values

• student_grades = {'Alice': [85, 90, 88], 'Bob': [78, 82, 85]}
• shopping_list = {'fruits': ['apple', 'banana', 'cherry'], 'vegetables': ['carrot', 'broccoli']}
• employee_projects = {'John': ['Project A', 'Project B'], 'Jane': ['Project C']}
• class_schedule = {'Monday': ['Math', 'Science'], 'Tuesday': ['English', 'History']}
• library = {'Fiction': ['1984', 'Brave New World'], 'Non-Fiction': ['Sapiens', 'Homo Deus']}

Dictionary Used to Find Common Elements

Dictionaries can be used to find common elements between different lists. By using the elements as keys and counting their occurrences, you can easily identify common elements.

Side Effects in Pseudocode for List in Dictionary

When working with lists in dictionaries, side effects can occur if you are not careful with how you modify the lists. Side effects refer to unintended changes to the data structure that can lead to bugs.

Example of Side Effects in Pseudocode

START
    DECLARE dictionary
    dictionary = {'key1': [1, 2], 'key2': [3, 4]}
    
    FUNCTION modify_list(dict, key, value)
        IF key IN dict THEN
            dict[key].APPEND(value)
        END IF
    END FUNCTION
    
    CALL modify_list(dictionary, 'key1', 5)
    PRINT dictionary  # Output: {'key1': [1, 2, 5], 'key2': [3, 4]}
    
    CALL modify_list(dictionary, 'key3', 6)
    PRINT dictionary  # Output: {'key1': [1, 2, 5], 'key2': [3, 4]}
END

In this example, the function modify_list modifies the list associated with a given key in the dictionary. If the key does not exist, no changes are made. This can lead to side effects if the function is called with keys that are not present in the dictionary.

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