Ontario high school credits explained: what the OSSD asks for

# Tally compulsory OSSD credits for a made-up student (ours, a teaching
# example of counting with conditions, not a graduation audit).
# Rules: ontario.ca, students who started Grade 9 in 2024 or later.
# Simplified: it ignores which grade each credit was earned in.

COMPULSORY = {"english": 4, "math": 3, "science": 2, "tech_ed": 1,
              "canadian_history": 1, "canadian_geography": 1, "arts": 1,
              "health_pe": 1, "french": 1, "career_studies": 0.5,
              "civics": 0.5}
STEM_GROUP = ["business", "computer_studies", "coop",
              "math", "science", "tech_ed"]   # math, science, tech_ed only beyond their own minimum

def tally(transcript):
    """transcript: list of (subject, credit) pairs. Returns totals."""
    totals = {}
    for subject, credit in transcript:
        totals[subject] = totals.get(subject, 0) + credit
    return totals

def check(transcript):
    totals = tally(transcript)
    missing = []
    for subject, needed in COMPULSORY.items():
        if totals.get(subject, 0) < needed:
            missing.append(subject + ": " + str(totals.get(subject, 0)) + " of " + str(needed))
    stem_ok = False
    for subject in STEM_GROUP:
        spare = totals.get(subject, 0) - COMPULSORY.get(subject, 0)
        if spare >= 1:            # a full credit left over after its own minimum
            stem_ok = True
    if not stem_ok:
        missing.append("STEM-related group: none yet")
    return missing


student = [("english", 1), ("english", 1), ("english", 1), ("english", 1),
           ("math", 1), ("math", 1), ("math", 1), ("science", 1), ("science", 1),
           ("tech_ed", 1), ("canadian_history", 1), ("canadian_geography", 1),
           ("arts", 1), ("health_pe", 1), ("french", 1),
           ("career_studies", 0.5), ("civics", 0.5)]

print(check(student))
student.append(("computer_studies", 1))     # ICS3U, say
print(check(student) or "all compulsory credits counted")

Output: first ['STEM-related group: none yet'], because the third math credit only fills the math line; then, with one computer studies credit added, all compulsory credits counted.