Lists are ordered, mutable collections of items. They allow duplicate elements and support various operations like indexing, slicing, appending, and deleting elements.
# Creating a list
fruits = ['apple', 'banana', 'cherry']
print(fruits)
# Indexing from the beginning (0-based)
print(fruits[0]) # apple
print(fruits[1]) # banana
print(fruits[2]) # cherry
# Indexing from the end (-1-based)
print(fruits[-1]) # cherry
print(fruits[-2]) # banana
print(fruits[-3]) # apple
Output:
['apple', 'banana', 'cherry']
apple
banana
cherry
cherry
banana
apple
Q: What is the index of 'banana' in the list fruits?
A: The index of 'banana' is 1 when indexed from the beginning, and -2 when indexed from the end.
print(fruits[1]) # banana
print(fruits[-2]) # banana
Output:
banana
banana
Lists are mutable, meaning you can change their content without changing their identity.
# Appending an item to the list
fruits.append('orange')
print(fruits)
Output:
['apple', 'banana', 'cherry', 'orange']
# Deleting an item from the list
del fruits[1]
print(fruits)
Output:
['apple', 'cherry', 'orange']
# Altering an item in the list
fruits[1] = 'blueberry'
print(fruits)
Output:
['apple', 'blueberry', 'orange']
Q: How can you find the length of a list in Python?
A: You can find the length of a list using the len() function.
# Finding the length of the list
print(len(fruits))
Output:
3
Dictionaries are unordered, mutable collections of key-value pairs. They are indexed by keys, which can be of any immutable type.
# Creating a dictionary
person = {'name': 'Alice', 'age': 25, 'city': 'New York'}
print(person)
Output:
{'name': 'Alice', 'age': 25, 'city': 'New York'}
Dictionaries are mutable, so you can change, add, or remove items.
# Adding a key-value pair
person['email'] = 'alice@example.com'
print(person)
Output:
{'name': 'Alice', 'age': 25, 'city': 'New York', 'email': 'alice@example.com'}
# Deleting a key-value pair
del person['age']
print(person)
Output:
{'name': 'Alice', 'city': 'New York', 'email': 'alice@example.com'}
# Altering a value
person['city'] = 'Los Angeles'
print(person)
Output:
{'name': 'Alice', 'city': 'Los Angeles', 'email': 'alice@example.com'}
Q: In the dictionary person, which are the keys and which are the values?
A: In the dictionary person:
Q: How can you check if a key exists in a dictionary?
A: You can check if a key exists in a dictionary using the in keyword.
# Checking if a key exists
print('name' in person)
print('age' in person)
Output:
True
False
Tuples are ordered, immutable collections of items. They allow duplicate elements and support indexing and slicing.
# Creating a tuple
colors = ('red', 'green', 'blue')
print(colors)
Output:
('red', 'green', 'blue')
Tuples are immutable, so you cannot change their content after creation.
# Accessing tuple elements
print(colors[1])
Output:
green
Q: How can you find the index of an element in a tuple?
A: You can find the index of an element in a tuple using the index() method.
# Finding the index of an element
print(colors.index('blue'))
Output:
2
Q: What happens if you try to alter a tuple?
A: Since tuples are immutable, attempting to alter their content will result in a TypeError.
# Attempting to alter a tuple
try:
colors[1] = 'yellow'
except TypeError as e:
print(e)
Output:
'tuple' object does not support item assignment