Chapter 2: Python Programming: Concepts I

Basics, Solutions

Oliver Bonham-Carter

Table of contents

• Welcome to Python Programming!
• Python Literals
• Variables and Operators
• Loops and Conditionals
• Squaring Algorithms
• Strings and Slicing
• Python Challenge Exercises
• Solutions to Challenge Exercises

Welcome to Python Programming!

Tip

Let’s make learning Python fun and practical!

What are literals?

Literals are fixed values in your code. They can be numbers, strings, booleans, etc.

Note

Examples: - 42 (integer) - 3.14 (float) - 'hello' (string) - True, False (boolean)

Python Code Sample

age = 18
pi = 3.14159
greeting = "Hello, world!"
is_active = True

Interesting Application

Use literals to set default values in games, apps, or data analysis scripts!

Python Literals

Literals are fixed values written directly in your code and are used to assign values to variables or as standalone values in expressions.

"""
This example shows different types of literals.
"""
integer_literal = 42        # An integer literal
float_literal = 3.14        # A floating-point literal
string_literal = "hello"    # A string literal
boolean_literal = True      # A boolean literal

print(integer_literal, float_literal, string_literal, boolean_literal)
# Output: 42 3.14 hello True

This code demonstrates how to use different types of literals in Python.

Variables and Operators

Variables store data for use in your program which can be manipulated by operators (e.g., addition, comparison, and assignment).

"""
This example shows how to use variables and operators.
"""
x = 10      # Assign 10 to x
y = 5       # Assign 5 to y
sum_xy = x + y         # Addition operator
diff_xy = x - y        # Subtraction operator
prod_xy = x * y        # Multiplication operator
is_equal = x == y      # Comparison operator
print(sum_xy, diff_xy, prod_xy, is_equal)
# Output: 15 5 50 False

This code uses variables and operators to do math and compare values.

Loops and Conditionals

Loops repeat actions. Conditionals let your code make decisions.

"""
This example prints numbers and checks if they are even or odd.
"""

for i in range(1, 6):  # Loop from 1 to 5
    if i % 2 == 0:     # Conditional: is i even?
        print(f"{i} is even")
    else:
        print(f"{i} is odd")
# Output:
# 1 is odd
# 2 is even
# and similar up to 5

This code loops through numbers and uses a conditional to check if each is even or odd.

Squaring Algorithms

Squaring means multiplying a number by itself. There are several ways to do this in Python.

"""
This example shows three ways to square a number.
"""
def square(n):
    """Returns the square of n."""
    return n * n

num = 7
squ1 = num * num         # Multiplication
squ2 = num ** 2          # Exponentiation

print(f"squ1: {squ1}, squ2: {squ2}, square(num): {square(num)}")
# Output: squ1: 49, squ2: 49, square(num): 49

This code demonstrates three ways to square a number in Python.

Strings and Slicing

Strings store text. Slicing lets you extract parts of a string.

"""
This example slices a string in different ways.
"""

text = "Python is awesome!"

first_word = text[:6]      # Get 'Python'
last_word = text[-8:]      # Get 'awesome!'
every_other = text[::2]    # Get every other character

print(first_word)    # Output: Python
print(last_word)     # Output: awesome!
print(every_other)   # Output: Pto saeo!

This code shows how to slice strings to get different parts or patterns.

Python Challenge Exercises

Try these programming challenges to practice your Python skills!

Challenge 1: Literal Mix-Up

Write code that uses at least three different types of literals (integer, float, string, boolean) and prints them in a single sentence.

# TODO

Challenge 2: Variable Math

Create two variables, perform addition, subtraction, multiplication, and division, and print the results with clear labels.

# TODO

Challenge 3: Loop & Conditional Fun

Write a loop that prints numbers from 1 to 10. For each number, print whether it is a multiple of 3 or not.

# TODO

Challenge 4: Squaring Game

Write a function that takes a number and returns both its square and its cube. Print the results for the number 5.

# TODO

Challenge 5: String Slicing Mystery

Given the string mystery = "QuartoPythonRocks!", print:

• The first 6 characters
• The last 5 characters
• Every third character

# TODO

Solutions to Challenge Exercises

Solution 1: Literal Mix-Up

integer = 7
float_num = 2.5
text = "apples"
is_fresh = True
print(f"I bought {integer} {text}, each cost {float_num} dollars. Fresh? {is_fresh}")

This code uses integer, float, string, and boolean literals in a sentence.

Solution 2: Variable Math

x = 12
y = 4
print(f"Addition: {x + y}")
print(f"Subtraction: {x - y}")
print(f"Multiplication: {x * y}")
print(f"Division: {x / y}")

This code performs math operations and prints results with labels.

Solution 3: Loop & Conditional Fun

for n in range(1, 11):
    if n % 3 == 0:
        print(f"{n} is a multiple of 3")
    else:
        print(f"{n} is not a multiple of 3")

This code loops through numbers and checks for multiples of 3.

Solution 4: Squaring Game

def square_and_cube(num):
    """Returns the square and cube of num."""
    return num ** 2, num ** 3

sq, cu = square_and_cube(5)
print(f"Square: {sq}, Cube: {cu}")

This function returns both the square and cube of a number.

Solution 5: String Slicing Mystery

mystery = "QuartoPythonRocks!"
print(mystery[:6])      # First 6 characters
print(mystery[-5:])     # Last 5 characters
print(mystery[::3])     # Every third character

This code slices the string in three different ways.