Day 1 — Solutions

Variables, types, strings, booleans, if statements

These are reference solutions. There’s often more than one right answer — if your version produces the same output, that’s what matters.

---

Exercise 1 — Variables and types

state = "Michigan"
population = 10_077_331
electoral_votes = 15

print(type(state))
print(type(population))
print(type(electoral_votes))

<class 'str'>
<class 'int'>
<class 'int'>

type() returns the class of the object.

---

Exercise 2 — Type conversion

vote_share_str = "52.3"
vote_share = float(vote_share_str)
margin = vote_share - (100 - vote_share)
print(f"Margin of victory: {margin:.1f} points")

Margin of victory: 4.6 points

Two-party share assumption means the other candidate got 100 - vote_share. Could also compute as 2 * vote_share - 100.

{margin.1f} looks weird, and isn’t something we covered in class. You don’t need it - it’s just rounding to the first decimal place for interpretability.

---

Exercise 3 — String indexing and slicing

name = "Senator Bernie Sanders"

print(name[0])         # 'S'
print(name[8:14])      # 'Bernie'
print(name[15:])       # 'Sanders'
print(name[-7:])       # 'Sanders' — same result, no counting required

S
Bernie
Sanders
Sanders

Negative indices count from the end. [-7:] is “give me everything from 7 characters before the end onward.”

---

Exercise 4 — f-strings

candidate = "Smith"
party = "Democratic"
vote_share = 0.523
state = "Ohio"

print(f"{candidate} ({party}) won {state} with {vote_share:.1%} of the vote.")

Smith (Democratic) won Ohio with 52.3% of the vote.

The format spec :.1% does two things: multiplies by 100 and rounds to one decimal place, then appends a %.

---

Exercise 5 — Boolean expressions

print(5 == 5.0)                  # True — Python compares numerically across int and float
print("Democrat" == "democrat")  # False — string equality is case-sensitive
print(60 > 50 and 60 < 70)       # True
print(not (50 > 100))            # True
print(0.49 + 0.51 == 1.0)        # False (!)

True
False
True
True
True

Computers store decimals in binary, and 0.49 and 0.51 don’t have exact binary representations — they’re approximations. The sum is very close to 1.0 but not exactly equal. Standard advice: when comparing floats, check whether the absolute difference is below a small tolerance, not strict equality. (abs(a - b) < 1e-9 is a common pattern.)

---

Exercise 6 — if / else

turnout = float(input("Enter turnout percentage: "))

if turnout > 60:
    print("High turnout")
elif turnout >= 40:
    print("Moderate turnout")
else:
    print("Low turnout")

---

Exercise 7 — Putting it together

candidate_a = "Adams"
candidate_b = "Burr"
candidate_c = "Carroll"

votes_a = 4_125
votes_b = 3_980
votes_c = 1_245

total = votes_a + votes_b + votes_c

share_a = votes_a / total
share_b = votes_b / total
share_c = votes_c / total

print(f"{candidate_a}: {share_a:.1%}")
print(f"{candidate_b}: {share_b:.1%}")
print(f"{candidate_c}: {share_c:.1%}")

if share_a > 0.50:
    print("Adams wins!")
else:
    print("Runoff required.")

Adams: 44.1%
Burr: 42.6%
Carroll: 13.3%
Runoff required.