Coding and AI classes in Magdeburg

import csv

days = []
with open("magdeburg_days.csv", encoding="utf-8") as f:
    for row in csv.DictReader(f):
        days.append((row["date"], float(row["mean"]), float(row["cloud"]), float(row["low"])))

pairs = []                       # today's weather, and did tomorrow freeze?
for today, tomorrow in zip(days, days[1:]):
    if -999 not in (today[1], today[2], tomorrow[3]):
        pairs.append((today[0], today[1], today[2], tomorrow[3] < 0))

train = [p for p in pairs if p[0] < "2020"]
test = [p for p in pairs if p[0] >= "2020"]

def score(rule, data):
    hits = sum(1 for p in data if rule(p) and p[3])
    misses = sum(1 for p in data if not rule(p) and p[3])
    alarms = sum(1 for p in data if rule(p) and not p[3])
    return hits, misses, alarms

# learn one number: the mean temperature below which we say "frost tomorrow"
chosen_t, fewest = None, None
for tenth in range(-100, 101):
    t = tenth / 10
    hits, misses, alarms = score(lambda p: p[1] <= t, train)
    if fewest is None or misses + alarms < fewest:
        chosen_t, fewest = t, misses + alarms

print("Training days:", len(train), " test days:", len(test))
print("Learned rule: frost tomorrow if today's mean is at or below", chosen_t, "C")
print("On the test years (hits, misses, false alarms):", score(lambda p: p[1] <= chosen_t, test))

It prints: Training days: 4981 test days: 2168, Learned rule: frost tomorrow if today's mean is at or below 2.8 C and On the test years (hits, misses, false alarms): (193, 113, 89).

# clear skies let heat escape at night: allow a warmer day to count when the sky is clearer
choice, fewest = None, None
for tenth in range(-100, 101):
    for step in range(0, 21):
        t, extra = tenth / 10, step / 10
        rule = lambda p: p[1] <= t + extra * (8 - p[2])
        hits, misses, alarms = score(rule, train)
        if fewest is None or misses + alarms < fewest:
            choice, fewest = (t, extra), misses + alarms

t, extra = choice
print("Two-number rule: base", t, "C, plus", extra, "C for every clear eighth of sky")
print("On the test years:", score(lambda p: p[1] <= t + extra * (8 - p[2]), test))
print("Frost nights in the test years:", sum(1 for p in test if p[3]), "of", len(test))

It prints: Two-number rule: base 1.2 C, plus 0.8 C for every clear eighth of sky, On the test years: (200, 106, 78) and Frost nights in the test years: 306 of 2168.