Tuples as dictionary keys

So far, we learned that keys have to be immutable and unique. We also saw examples of keys using integers and strings. Another data type we can use as keys is tuples. For instance, if we wanted to map some latitude and longitude coordinates to a city, we can map some tuple with the format, (latitude, longitude), as a key to a string city. Notice that the type of keys are tuples and the values are strings.

cities = {(32.7157, 117.1611): 'San Diego', (37.7749, 122.4194): 'San Francisco',
          (40.7128, 74.006): 'New York', (30.2672, 97.7431): 'Austin'}

Tuples as Values

Tuples can also be used as values. Instead of creating a dictionary mapping latitude and longitude coordinates to a city, we can do the reverse by mapping a city to a coordinate. Notice that the type of the keys are strings and the values are tuples.

coordinates = {'San Diego': (32.7157, 117.1611), 'San Francisco': (37.7749, 122.4194),
               'New York': (40.7128, 74.006), 'Austin': (30.2672, 97.7431)}

Dictionary of Colors

Now that we’ve learned that we can use tuples for keys and values, another dictionary that would be really helpful is a dictionary of colors associated with their tuple values. Below is a colors dictionary that uses the names of the colors, which are strings, as keys that are mapped to their RGB tuple values.

colors = {'red': (255, 0, 0), 'green': (0, 255, 0), 'blue': (0, 0, 255), 'yellow': (255, 255, 0),
          'violet': (238, 130, 238), 'orange': (255, 165, 0), 'indigo': (75, 0, 130)}

If we wanted to create a rainbow stripe, we can do so by using the color dictionary we created. This is much more easier to visualize than if we saw a 2D list of RGB tuples.

rainbow = [[colors['red'], colors['orange'], colors['yellow'], colors['green'],
            colors['blue'], colors['indigo'], colors['violet']]]