A Complete Beginner’s Introduction to Python
Part 9
Dictionaries
A dictionary is another way to store data in Python. Dictionaries have keys and values. To create a dictionary you use the curly braces syntax {}.
Here’s how we create a dictionary with a few values and assign it to the variable names_and_numbers:
names_and_numbers = {
'Fernando': 'Ok',
'Prince': 'Amazing',
'The Artist Formerly Known as Prince': 'Awesome',
2: "Hello",
"Goodbye": 12.6,
}
We can reference dictionaries in a similar way to how we reference tuples and lists. With those, we referenced the position in the list or tuple. In this case, we can reference the key.
For example, names_and_numbers['Fernando'] would give us the string: 'Ok'. And if we used the key of 2, we get 'Hello', not 'Prince' or 'Amazing'.
But we don’t have to start knowing what everything inside our dictionary will be. We can start an empty dictionary and go from there:
friends_numbers = {}
friends_numbers["James"] = "333-666-8999"
friends_numbers["Hugo"] = "555-111-3232"
print(friends_numbers)
friends_numbers["Che"] = "777-222-4545"
print(friends_numbers)
pop and Dictionaries
Similarly to lists, you can pop elements off the dictionary:
friends_numbers.pop("James")
This will return James’ number and remove him and his number from the dictionary.
Dictionary keys() and values()
You can also get all the keys from a dictionary by adding .keys() to the end or all the values by adding a .values(). Both of these will return an object that you can iterate over but that you can’t manipulate in the same way as a list unless you explicitly change it into one with list().
friends_numbers.keys()
result = friends_numbers.values()
result[0] # This will fail
new_result = list(result)
new_result[0] # This will work!