rain_prob.py

#!/usr/bin/env python3

from functools import reduce
from operator import mul

# the probability that it will rain in the next hour
rain_probs = {
    1200: 0.05,
    1300: 0.05,
    1400: 0.05,
    1500: 0.05,
    1600: 0.06,
    1700: 0.09,
    1800: 0.13,
    1900: 0.18,
    2000: 0.22,
    2100: 0.26,
    2200: 0.31,
    2300: 0.35,
}

# inverse: probability that it won't rain in the next hour
no_rain_probs = {h: 1.0 - p for h, p in rain_probs.items()}
print(no_rain_probs)

# accumulated: probability that it never rains until the next hour
acc_p = 1.0
no_rain_acc_probs = {}
for hour, prob in no_rain_probs.items():
    acc_p *= prob
    no_rain_acc_probs[hour] = acc_p
print(no_rain_acc_probs)


# same as above, but calculated in a function
def calc_acc_probs(prob_dict):
    acc_p = 1.0
    acc_probs = {}
    for k, p in prob_dict.items():
        acc_p *= p
        acc_probs[k] = acc_p
    return acc_probs

print(calc_acc_probs(no_rain_probs))

# same as above, but using a functional style
probs = list(reduce(lambda l, r: l + [l[-1]*r], no_rain_probs.values(), [1.0])[1:])
no_rain_acc_probs = dict(zip(no_rain_probs.keys(), probs))
print(no_rain_acc_probs)