What are Dictionaries?

Dictionaries are another type of data structure. They are used to associate a unique id with its value. This association is referred to as a key-value pair.

A Weakness of Lists

Recall that with lists, our indices had to be integers. You will soon see with dictionaries that our indices do not have to be integers.

How can I create a Dictionary?

Easy. Here is an example on creating an empty dictionary:

a = {}

Do NOT confuse this syntax with the syntax for creating a list: a = []

Dictionary representing users at a bank:

Ross = {'Name': 'Ross', 'ID': 1234567890, 'Money': 4000.00}
Joey = {'Name': 'Joey', 'ID': 0987654321, 'Money': 222.30}

The key is the string to the left of the colon. Its respective value is the element to the right of the colon. In the example above, the key include: Name, ID & Money.

How do I access elements in the Dictionary?

Unlike lists, you can index dictionaries with strings. For example:

Ross['Name'] ==> Ross
Joey['ID'] ==> 0987654321
Joey['Money'] ==> 222.30

Updating Elements in a List

To update how much money someone has in their account, you use the same indexing structure. For example:

Ross['Money'] = 5000

While Loops

Last module, we learned about For loops. This week, we will learn about While loops.

x = 10
while (x > 0):
	print x
	x -= 1

What do you think the line above code above will print?

x = 10
while (x > 0):
	print x

How about now? What will this modified code print?

Activity - You are the banker

You are a banker at the biggest bank in the country. 6 friends come up to you and ask you to update various items relating to their accounts. Please help them. Each bank account is a dictionary that looks like the following:

Ross = {'Name': 'Ross', 'ID': 1234567890, 'Checking': 4000.00, 'Savings': 2200.89}

Activity Steps:

1. git clone https://github.com/icodecamp/module5_banking.git

2. cd module5_banking

3. Run: python banking.py.

4. Follow the directions that the script tells you