1. COSC 1323 – Computer Science Concepts I
Python Dictionaries
COSC 1323 – Computer Science Concepts I

2. Dictionary Description
A list is a sequence of indexed objects. Each item has an associated index number
Unlike a list, a dictionary is indexed by keys, which can be any immutable type (i.e., the key cannot be changed)
Think of dictionaries as an unordered set of key:value pairs
In other languages, dictionairies may be called “associative arrays”

3. Dictionary Description
A pair of braces creates an empty dictionary: {}
Placing a comma-separated list of key:value pairs within the braces adds initial key:value pairs to the dictionary\
The main operations on a dictionary are storing a value with some key and extracting the value given the key
To check wether a single key is in the dictionary, use the ‘in’ keyword

4. Dictionary Examples
es.txt