A tuple is a sequence of objects. It can have any number of objects inside. In Python tuples are written with round brackets ().
latitude = 37.7739
longitude = -121.5687
coordinates = (latitude, longitude)
print(coordinates)You can access each item by its position, i.e. index. In programming, the counting starts from 0. So the first item has an index of 0, the second item an index of 1 and so now. The index has to be put inside square brackets [].
y = coordinates[0]
x = coordinates[1]
print(x, y)A list is similar to a tuple - but with a key difference. With tuples, once created, they cannot be changed, i.e. they are immutable. But lists are mutable. You can add, delete or change elements within a list. In Python, lists are written with square brackets []
cities = ['San Francisco', 'Los Angeles', 'New York', 'Atlanta']
print(cities)You can access the elements from a list using index the same way as tuples.
print(cities[0])You can call len() function with any Python object and it will calculates the size of the object.
print(len(cities))We can add items to the list using the append() method
cities.append('Boston')
print(cities)As lists are mutable, you will see that the size of the list has now changed
print(len(cities))Another useful method for lists is sort() - which can sort the elements in a list.
cities.sort()
print(cities)The default sorting is in ascending order. If we wanted to sort the list in a decending order, we can call the function with reverse=True
cities.sort(reverse=True)
print(cities)Sets are like lists, but with some interesting properties. Mainly that they contain only unique values. It also allows for set operations - such as intersection, union and difference. In practice, the sets are typically created from lists.
capitals = ['Sacramento', 'Boston', 'Austin', 'Atlanta']
capitals_set = set(capitals)
cities_set = set(cities)
capital_cities = capitals_set.intersection(cities_set)
print(capital_cities)Sets are also useful in finding unique elements in a list. Let's merge the two lists using the extend() method. The resulting list will have duplicate elements. Creating a set from the list removes the duplicate elements.
cities.extend(capitals)
print(cities)
print(set(cities))In Python dictionaries are written with curly brackets {}. Dictionaries have keys and values. With lists, we can access each element by its index. But a dictionary makes it easy to access the element by name. Keys and values are separated by a colon :.
data = {'city': 'San Francisco', 'population': 881549, 'coordinates': (-122.4194, 37.7749) }
print(data)You can access an item of a dictionary by referring to its key name, inside square brackets.
print(data['city'])From the dictionary below, how do you access the latitude and longitude values? print the latitude and longitude of new york city by extracting it from the dictionary below.
The expected output should look like below.
40.661
-73.944
nyc_data = {'city': 'New York', 'population': 8175133, 'coordinates': (40.661, -73.944) }