Nested dictionaries

Definition

A nested dictionary is a dictionary within another dictionary. It allows for hierarchical data structures where values can themselves be dictionaries.

5 Must Know Facts For Your Next Test

1. Nested dictionaries are useful for representing complex data structures like JSON.
2. Accessing an element in a nested dictionary requires multiple keys.
3. You can add, modify, or delete elements in nested dictionaries just like with standard dictionaries.
4. The 'in' keyword checks for key presence at the top level, but nested checks require more detailed examination.
5. Dictionary comprehension can be used to create or manipulate nested dictionaries.

Review Questions

• How do you access a value in a nested dictionary using multiple keys?
• What Python syntax would you use to check if a certain key exists in the top level of a nested dictionary?
• Give an example of how you would add a new sub-dictionary to an existing dictionary.

Related terms

Dictionary: A collection of key-value pairs where each key is unique and maps to a value.

Dictionary Comprehension: A concise way to create dictionaries using an iterable, often used with loops and conditionals.

JSON: $\text{JavaScript Object Notation (JSON)}$ is a lightweight data-interchange format that uses human-readable text to store and transmit data objects consisting of attribute-value pairs and arrays.