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Assignment

Weekend Assignment 2

No new material is introduced this weekend. This assignment combines

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Weekend Assignment 2#

Week 2 Synthesis: while/for Loops, Nesting, Approximation, and Patterns#

No new material is introduced this weekend. This assignment combines everything from Days 6–10 into longer, more realistic programs, and connects back to Week 1 (branching, strings). Expect this to take 2–4 hours total across Saturday and Sunday — likely a bit longer than Weekend 1, since loops are a meaningfully bigger jump in complexity.

Create a new file called weekend2_solutions.py and write all of your answers there, clearly labeled by part and exercise number.

Part A: Guided Synthesis (Saturday)#

A1. Prime Number Checker (combines: while/for loops, branching, flags)#

Write a program that:

  1. Asks the user for a positive integer n
  2. Uses a loop and a flag to determine whether n is prime (a prime number has no divisors other than 1 and itself)
  3. Prints "n is prime" or "n is not prime"

Hints:

  • A number n is prime if no integer from 2 to n - 1 divides it evenly
  • You can stop checking once you find ANY divisor — use break
  • Handle the edge cases: numbers less than 2 are not prime by definition
  • For efficiency (optional bonus), you only need to check divisors up to the square root of n, since if n = a * b with a <= b, then a <= sqrt(n)

Test with: 2 (prime), 17 (prime), 18 (not prime), 1 (not prime), 97 (prime)

A2. Number Pyramid (combines: nested loops, f-strings)#

Write a program that asks the user for a number of rows n, then prints a centered number pyramid like this (shown for n=5):

    1
   222
  33333
 4444444
555555555

Each row i (starting from 1) should contain 2*i - 1 copies of the digit i, centered using spaces. (Hint: f-string centering with ^ from Week 1, or build the padding manually with string repetition.)

A3. Word Frequency in a Sentence (combines: nested loops, string#

processing, the counting pattern)

Write a program that:

  1. Takes a sentence as input
  2. For a specific target word the user also provides, counts how many times that word appears as a SUBSTRING anywhere in the sentence (case-insensitive — you can use .lower() on both, which we briefly saw in Week 1's preview, or simply compare both already-lowercased)
  3. Prints the count

Test with: sentence = "the cat sat on the mat with another cat", target = "cat" (expected count: 2)

Part B: Independent Application (Saturday or Sunday)#

B1. Simple Number Guessing Game (combines: while loop, sentinel#

pattern, branching)

Write a complete number guessing game:

  1. Hard-code a secret number (e.g., secret = 63)
  2. Use a while loop that keeps asking the user to guess until they get it right
  3. After each wrong guess, tell them "Too low!" or "Too high!"
  4. Count how many guesses it took, and print that count once they win
  5. Bonus: limit them to a maximum of 7 guesses; if they run out, reveal the secret number and end the game gracefully

B2. Digit Sum and Digital Root (combines: while loop, % and //#

from Week 1, accumulator pattern)

Write a program that:

  1. Asks the user for a positive integer
  2. Computes the sum of its digits using a while loop (don't convert to a string — use % and // as in Week 1's challenge problems)
  3. Repeats this process on the resulting sum, again and again, until the result is a single digit (this final single-digit result is called the "digital root")
  4. Prints each intermediate sum along the way, then the final digital root

Example: 9875 → 9+8+7+5=29 → 2+9=11 → 1+1=2. Digital root: 2

Part C: Cumulative Review and Reflection (Sunday)#

C1. Mixed Review Questions#

Answer these without running code first — write your answers, THEN verify in Python.

  1. Trace this and write the EXACT output, line by line:
   for i in range(3):
       for j in range(2):
           if i == j:
               continue
           print(i, j)
  1. What's the difference between these two loops? Do they produce the same final value of total?
   # Version A
   total = 0
   for i in range(5):
       total += i

   # Version B
   total = 1
   for i in range(5):
       total += i
  1. Explain in your own words (2-3 sentences) why 0.1 + 0.1 + 0.1 == 0.3 evaluates to False in Python, connecting this back to Week 1's discussion of floating-point types.
  1. Write the chained-condition version of: "keep looping while count is less than 10 AND found is False" as a single while condition.
  1. What's wrong with this code, and what would actually happen if you ran it? (Don't run it — reason through it.)
   n = 1
   while n != 10:
       print(n)
       n += 2

C2. Bug Hunt#

Each snippet below has exactly one bug. Identify it (as a comment) and write the corrected version.

# Snippet 1
total = 0
for i in range(1, 10):
    total = i
print(total)
# (intended to compute the sum of 1 through 9)
# Snippet 2
n = 5
while n > 0:
    print(n)
    n += 1
# Snippet 3
for i in range(3):
    for j in range(3):
        if i == j:
            break
    print(i, j)
# (intended to print i, j pairs only when the inner loop completes
#  fully without finding i==j -- but the print is misplaced and j
#  refers to a leftover value)
# Snippet 4
factorial = 0
for i in range(1, 6):
    factorial *= i
print(factorial)
# (intended to compute 5! = 120)

C3. Reflection (write 4-6 sentences)#

In your own words, answer:

  • Loops were described as "the biggest conceptual jump so far." Do you agree? What part of loops took the most effort to understand?
  • Of the six loop patterns cataloged in Chapter 10 (counting, accumulating, building, search-and-report, extreme-value, ALL/ANY), which one do you feel most confident applying to a brand-new problem?
  • Write one nested-loop bug you made this week (or almost made) and how you caught it.

Write your reflection in 09_PROGRESS_TRACKER/week_02_tracker.md under the Reflection section.

Self-Check Before Moving to Week 3#

  • [ ] All 5 daily quizzes attempted and reviewed
  • [ ] Part A (A1, A2, A3) completed and runs without errors
  • [ ] Part B (B1, B2) completed and runs without errors
  • [ ] Part C (C1, C2, C3) completed
  • [ ] Progress tracker filled in
  • [ ] You can explain, without notes, the three required parts of a counting while loop
  • [ ] You can explain, without notes, why range(5) does NOT include 5
  • [ ] You can trace a nested loop by hand and correctly predict every line it prints
  • [ ] You can explain the difference between break and continue without looking at examples
  • [ ] You can write a search-and-report loop (flag + break) from scratch

If you checked all the boxes, you're ready for Week 3: Functions.