dictionary

• dictionaries are fundamental data structures used to store collections of items in a key-value format. Unlike lists and sets, which store items in an order, dictionaries provide a flexible way to associate unique keys with their corresponding values.
• Dictionaries are enclosed in curly braces {} with key-value pairs separated by colons :
• Keys must be unique and immutable (strings, numbers, or tuples are common choices for keys).
• Values can be of any data type (strings, integers, lists, or even other dictionaries).
• You can access a value by its associated key within square brackets
• If the key doesn't exist, a KeyError is raised.
• Adding or Removing Elements
  • Dictionaries are mutable, allowing you to modify their contents after creation
    • my_dict[key] = value: Add a new key-value pair or modify an existing value for a key.
    • del my_dict[key]: Remove the key-value pair associated with a specific key.
• Common Dictionary Methods
  • len(my_dict): Returns the number of key-value pairs in the dictionary.
  • get(key, default): Returns the value for a key, or a default value if the key is not found.
  • keys(): Returns a view of all the keys in the dictionary as a dictionary view object.
  • values(): Returns a view of all the values in the dictionary as a dictionary view object.
  • items(): Returns a view of all the key-value pairs in the dictionary as a dictionary view object (tuples of (key, value)).
  • pop(key, default): Removes the key-value pair for a key and returns the value. If the key is not found, it returns the default value (if provided).
  • popitem(): Removes and returns an arbitrary key-value pair from the dictionary.
• When to Use Dictionaries
  • Use dictionaries when you need to associate data with unique identifiers or labels.
  • They are well-suited for storing configuration settings, user preferences, or any data where you need to retrieve information based on a key.
  • Dictionaries are essential for building more complex data structures and relationships between data elements in your programs.
• Key Points
  • Dictionaries provide a flexible way to store key-value pairs.
  • Keys must be unique and immutable.
  • Values can be of any data type.
  • Use methods to add, remove, access elements, and iterate over keys, values, or key-value pairs.

fruits = {"apple": "red", "banana": "yellow", "cherry": "red"}

apple_color = fruits["apple"]  # apple_color will be "red"

fruits = {"apple": "red", "banana": "yellow", "cherry": "red"} apple_color = fruits["apple"] # apple_color will be "red"