Grade Letter

Write a function that converts a numeric score into a letter grade.

grade_letter(score)

90 and above → "A"
80 to 89 → "B"
70 to 79 → "C"
60 to 69 → "D"
below 60 → "F"

Examples

grade_letter(95)   // → "A"
grade_letter(72)   // → "C"
grade_letter(40)   // → "F"
grade_letter(90)   // → "A"   (boundary is inclusive)

Walkthrough

Thinking it through

The key insight is ordering: check the highest threshold first, and let elif do the work of excluding everything above it.

def grade_letter(score):
    if score >= 90:
        return "A"
    elif score >= 80:
        return "B"
    elif score >= 70:
        return "C"
    elif score >= 60:
        return "D"
    else:
        return "F"

Because conditions are checked top to bottom and the first match wins, by the time Python reaches elif score >= 80, it already knows score < 90 (otherwise the first branch would have returned already). So score >= 80 at that point effectively means "between 80 and 89" — you don't need to write score >= 80 and score < 90 explicitly.

If you checked from the bottom up instead (score >= 60 first), you'd need explicit upper bounds everywhere, since a 95 would incorrectly match score >= 60 first. Ordering from highest to lowest sidesteps that entirely.

main.py

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