Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

Accessing Ingredients: output all the ingredients from the following list within the “ingredients” key using a for loop:

>>> pizza = {
>>> 'ingredients': ['cheese', 'sausage', 'peppers']
>>> }

Data collections allow us to work with large data as they are stored in key-value pairs. remember that data is accessed through keys.
Tuesday: Working with Dictionaries
Today’s lesson will cover how to add data, manipulating data, removing key-value pairs, and iterating through dictionaries.
To follow along with this lesson, let’s continue from our previous notebook file
“Week_06” and simply add a markdown cell at the bottom that says, “Working with Dictionaries.”

Adding New Information

You’ll often need to add new key-value pairs after declaring a dictionary. Let’s see how:

# adding new key/value pairs to a dictionary car = { "year": 2018 } car["color"] = "Blue" print( "Year: { } \t Color: { }".format( car["year"], car["color"] ) )

Go ahead and run the cell. To add new pairs, on the left side of the equals operator, you provide the dictionary name, followed by the new key within brackets. On the right side is whatever you want the value to be. This will output a nicely formatted string with our car information.
Note as of python, 3.7 dictionaries are ordered by default. in older versions of python, key-value pairs didn’t always keep their order. You would have needed to use an OrderedDict( ).

Changing Information

Altering key-value pairs is exactly like adding a new pair. If the key exists, it simply overwrites the previous value; however, if it doesn’t exist, it will create a new key-value pair for you:

# updating a value for a key/value pair that already exists car = { "year": 2018, "color": "Blue" } car["color"] = "Red" print( "Year: { } \t Color: { }".format( car["year"], car["color"] ) )

Go ahead and run the cell. Like how we declared a new key-value pair earlier, since the key “color” already exists in the dictionary, it simply overwrites the previous value.