Advanced Python · Week 1

List Review and Algorithms

Step 1 of 5

Exercise 1: List Terminology Review

Welcome to Python 2! Let's start by reviewing some important list terminology.

Key List Terms

List: An ordered, mutable collection of elements.
Index: The position of an element in a list (starting from 0).
Slice: A portion of a list, specified by a range of indices.
Nested List: A list that contains other lists as elements.

Let's practice working with these concepts. Your task is to create a list, access elements, and perform slicing.

# Create a list of fruits
fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry']

# Print the third fruit (remember, indexing starts at 0)
print(fruits[2])

# Print a slice of the list (from index 1 to 3, not including 3)
print(fruits[1:3])

# Print the last fruit using negative indexing
print(fruits[-1])

Now it's your turn! Modify the code above to:

Add 'fig' to the end of the list
Print the first and last two fruits using slicing
Print the list in reverse order

Type your code in the editor below, then hit the Run button to see if it works!

Starter code

# Modify the list and print as instructed
fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry']

# Your code here

Write your code here

python

# Modify the list and print as instructed
fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry']

# Your code here

Exercise 2: Working with 2D Arrays

In Python, we can create 2D arrays (or matrices) using nested lists. Let's explore how to work with them.

2D Array Basics

A 2D array is a list of lists. Each inner list represents a row in the matrix.

To access an element: matrix[row][column]

Here's an example of creating and accessing elements in a 2D array:

# Create a 3x3 matrix
matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

# Print the entire matrix
print(matrix)

# Print the second row
print(matrix[1])

# Print the element at the second row, third column
print(matrix[1][2])

Now it's your turn! Create a 4x4 matrix representing a tic-tac-toe board with 'X', 'O', and empty spaces (' '). Then:

Print the entire board
Print the third row
Replace the center element with an 'X' and print the updated board

Write your code in the editor below and run it to see the results!

Starter code

# Create and manipulate a 4x4 tic-tac-toe board

# Your code here

Write your code here

python

# Create and manipulate a 4x4 tic-tac-toe board

# Your code here

Exercise 3: List Iteration Algorithms

Iterating through lists is a fundamental skill in Python. Let's explore different ways to do this.

Iteration Methods

Using a for loop with elements
Using a for loop with indices
Using enumerate() for both index and value

Here are examples of different iteration methods:

numbers = [1, 2, 3, 4, 5]

# Method 1: Iterate through elements
for num in numbers:
    print(num)

# Method 2: Iterate using indices
for i in range(len(numbers)):
    print(f"Index {i}: {numbers[i]}")

# Method 3: Using enumerate
for index, value in enumerate(numbers):
    print(f"Index {index}: {value}")

Your task is to write a function that finds the sum and product of all elements in a list. Then, use this function on the list [1, 2, 3, 4, 5] and print the results.

Write your code in the editor below and run it to check your solution!

Starter code

def sum_and_product(numbers):
    # Your code here
    pass

# Test your function
numbers = [1, 2, 3, 4, 5]
# Call your function and print the results

Write your code here

python

def sum_and_product(numbers):
    # Your code here
    pass

# Test your function
numbers = [1, 2, 3, 4, 5]
# Call your function and print the results

Exercise 4: List Comprehensions

List comprehensions provide a concise way to create lists in Python. They can often replace loops and map() calls with more readable and efficient code.

List Comprehension Syntax

[expression for item in iterable if condition]

expression: What to put in the new list
item: A variable representing each element in the iterable
iterable: The list, tuple, or other iterable to loop over
condition: Optional. Only include items that meet this condition

Here are some examples of list comprehensions:

# Create a list of squares
squares = [x**2 for x in range(10)]
print(squares)

# Create a list of even numbers
evens = [x for x in range(20) if x % 2 == 0]
print(evens)

# Create a list of tuples (number, square) for odd numbers
odd_squares = [(x, x**2) for x in range(10) if x % 2 != 0]
print(odd_squares)

Your task is to use list comprehensions to:

Create a list of the first 10 powers of 2 (2^0 to 2^9)
Create a list of all numbers from 1 to 50 that are divisible by 3 or 5
Create a list of tuples (x, y) for all x from 1 to 5 and all y from 6 to 10

Write your code in the editor below and run it to check your solutions!

Starter code

# Your list comprehensions here

# 1. Powers of 2

# 2. Numbers divisible by 3 or 5

# 3. Tuples (x, y)

Write your code here

python

# Your list comprehensions here

# 1. Powers of 2

# 2. Numbers divisible by 3 or 5

# 3. Tuples (x, y)

Weekly Project: Matrix Operations

For this week's project, you'll create a set of functions to perform basic matrix operations. This will help reinforce your understanding of 2D arrays and list manipulation.

Your task is to implement the following functions:

print_matrix(matrix): Neatly print a matrix
matrix_addition(matrix1, matrix2): Add two matrices
matrix_scalar_multiply(matrix, scalar): Multiply a matrix by a scalar
matrix_transpose(matrix): Transpose a matrix

Here's a starting template with some test cases:

def print_matrix(matrix):
    # Your code here
    pass

def matrix_addition(matrix1, matrix2):
    # Your code here
    pass

def matrix_scalar_multiply(matrix, scalar):
    # Your code here
    pass

def matrix_transpose(matrix):
    # Your code here
    pass

# Test matrices
matrix_a = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
matrix_b = [[9, 8, 7], [6, 5, 4], [3, 2, 1]]

# Test your functions
print("Matrix A:")
print_matrix(matrix_a)

print("
Matrix B:")
print_matrix(matrix_b)

print("
Matrix A + B:")
result = matrix_addition(matrix_a, matrix_b)
print_matrix(result)

print("
Matrix A * 2:")
result = matrix_scalar_multiply(matrix_a, 2)
print_matrix(result)

print("
Transpose of Matrix A:")
result = matrix_transpose(matrix_a)
print_matrix(result)

Implement the functions in the code editor below. Make sure to handle potential errors, such as matrices of different sizes for addition. When you're done, run your code to test all the functions.

This project will give you hands-on experience with 2D arrays and help you practice the list manipulation techniques we've covered this week. Good luck!

Starter code

# Implement your matrix operations here

def print_matrix(matrix):
    # Your code here
    pass

def matrix_addition(matrix1, matrix2):
    # Your code here
    pass

def matrix_scalar_multiply(matrix, scalar):
    # Your code here
    pass

def matrix_transpose(matrix):
    # Your code here
    pass

# Test matrices
matrix_a = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
matrix_b = [[9, 8, 7], [6, 5, 4], [3, 2, 1]]

# Your test code here

Write your code here

python

# Implement your matrix operations here

def print_matrix(matrix):
    # Your code here
    pass

def matrix_addition(matrix1, matrix2):
    # Your code here
    pass

def matrix_scalar_multiply(matrix, scalar):
    # Your code here
    pass

def matrix_transpose(matrix):
    # Your code here
    pass

# Test matrices
matrix_a = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
matrix_b = [[9, 8, 7], [6, 5, 4], [3, 2, 1]]

# Your test code here

NextDictionaries