Course Content
Introduction to Python
Introduction to Python
What Is a Dictionary?
In previous chapters, we dove into data structures that rely on numeric indices. Now, we're going to explore a structure that uses a key — whether it's a string, tuple, number, and so on — to index its values. This structure is known as a dictionary. Within dictionaries, data is stored in key-value pairs. Here are some key points to remember about dictionary keys:
- You can use any immutable type as a dictionary key;
- Tuples can serve as keys, but only if they contain strings, numbers, or other tuples;
- A single dictionary won't have duplicate keys;
- In Python, dictionaries are enclosed within curly brackets
{}
.
To illustrate, let's say we want to capture data about countries. The dictionary could use country names as keys, with corresponding values (like area and population) saved as tuples.
# Create dictionary countries_dict = {'USA': (9629091, 331002651), 'Canada': (9984670, 37742154), 'Germany': (357114, 83783942)} print(countries_dict)
Got it? So, how do you retrieve a particular item from a dictionary? As touched upon earlier, you reference an item in a dictionary using its key. If the key is a string (as in our example), remember to wrap it in quotation marks. Just like with list or tuple indices, you'll place the key inside square brackets.
# Dictionary countries_dict = {'USA': (9629091, 331002651), 'Canada': (9984670, 37742154), 'Germany': (357114, 83783942)} # Information about Canada print(countries_dict["Canada"])
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