1. Keys:
* Function: Keys are unique identifiers used to access the corresponding value. They act like labels or pointers within the dictionary.
* Characteristics:
* Unique: Each key must be distinct.
* Immutable: Typically keys cannot be changed once assigned (though this can vary depending on the specific dictionary implementation).
* Hashable: Keys need to be hashable, meaning they can be converted into a unique hash value. This makes it efficient to find values based on their keys.
2. Values:
* Function: Values are the information associated with each key. They hold the actual data you want to store in the dictionary.
* Characteristics:
* No restrictions: Values can be of any data type, including numbers, strings, lists, other dictionaries, and even functions.
* Mutable: Values can be changed or updated after they are assigned.
3. Key-Value Pairs:
* Function: The fundamental building blocks of a dictionary. Each key-value pair links a specific key to its corresponding value.
4. Dictionary Structure:
* Function: This is the underlying organization of how key-value pairs are stored and accessed.
* Implementation: Depending on the programming language, dictionaries can be implemented using various techniques like hash tables or trees, which impact their performance and how they handle collisions (when two keys have the same hash value).
Example:
Imagine a dictionary storing information about students:
```python
student_info = {
"name": "Alice",
"age": 20,
"major": "Computer Science"
}
```
Here:
* Keys: `name`, `age`, `major`
* Values: `"Alice"`, `20`, `"Computer Science"`
You can access Alice's age using the key `age`:
```python
student_info["age"] # Output: 20
```
Key Takeaways:
* Dictionaries are efficient for storing and retrieving data based on unique keys.
* The combination of keys and values allows you to create flexible and structured data representations.
* Understanding the key-value pair structure is essential for working effectively with dictionaries.