Weekend Assignment 3#

Week 3 Cumulative Review (Saturday Morning)#

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This weekend is structured differently from Weeks 1–2. Instead of a full assignment, you'll complete a shorter cumulative review here (aim for about an hour), and then spend the majority of your weekend on Mini-Project 1 in 05_MINI_PROJECTS/week_03/ — this course's first complete, multi-function program.

Create a file called weekend3_review_solutions.py for your answers below.

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Part A: Tracing Multi-Function Programs#

A1. Full Trace#

Trace this program completely, writing out the value of every variable at every step, before running it:

def add_five(x):
    return x + 5

def double(x):
    return x * 2

def mystery(x):
    a = add_five(x)
    b = double(a)
    c = add_five(b)
    return c

print(mystery(3))

A2. Scope Trace#

Trace this program and explain, in a comment, exactly why it prints what it prints:

value = 100

def update(value):
    value = value + 1
    return value

new_value = update(value)
print(value, new_value)

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Part B: Writing Functions From a Specification#

B1. Spec-First Design#

Given ONLY this specification (no implementation), write the function:

def days_to_hours(days):
    """
    Assumes: days is a non-negative number
    Returns: the equivalent number of hours
    """
    # YOUR IMPLEMENTATION HERE

B2. Decomposition Practice#

Decompose this single function into at least two well-named, well- specified helper functions, then a top-level function that uses them:

def shipping_cost(weight_kg, distance_km, express):
    base_cost = weight_kg * 0.5 + distance_km * 0.01
    if express:
        base_cost = base_cost * 1.5
    return round(base_cost, 2)

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Part C: Bug Hunt#

Each snippet below has exactly one bug related to this week's material. Identify it (as a comment) and write the corrected version.

# Snippet 1
def add(a, b):
    print(a + b)

total = add(3, 4) + add(5, 6)
print(total)

# Snippet 2
def f(x, y=10, z):
    return x + y + z

# Snippet 3
count = 0

def increment():
    count = count + 1
    return count

print(increment())

# Snippet 4
def get_grade(score):
    if score >= 90:
        return "A"
    if score >= 80:
        return "B"
    # missing cases for 70+, 60+, and below 60!

print(get_grade(65))

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Part D: Reflection (write 3-5 sentences)#

In your own words, answer:

• What's the most important difference between print and return that you'll need to remember going forward?
• Which felt more natural this week: writing a function's specification BEFORE implementing it, or writing the implementation first and adding a docstring afterward? Why do you think that is?

Write your reflection in 09_PROGRESS_TRACKER/week_03_tracker.md under the Reflection section.

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Self-Check Before Starting the Mini-Project#

• [ ] All 5 daily quizzes attempted and reviewed
• [ ] Parts A, B, C, D above completed
• [ ] You can explain, without notes, the difference between a parameter and an argument
• [ ] You can explain, without notes, why return is usually preferable to print inside a function meant to compute a reusable value
• [ ] You can trace a program with at least 3 functions calling each other and correctly predict its output

Once you've checked these boxes, move on to Mini-Project 1: 05_MINI_PROJECTS/week_03/README.md