day2.py

def is_increasing(a, b):
    return b - a > 0 and b - a <= 3
def is_decreasing(a, b):
    return b - a < 0 and b - a >= -3
def is_unsafe(list, bad_level):
    n1 = int(list[0])
    n2 = int(list[1])
    if is_increasing(n1, n2):
        last_n = n2
        for n in list[2:]:
            if not (is_increasing(last_n, int(n))):
                if bad_level:
                    return True
                else:
                    bad_level = True
            else:
                last_n = int(n)
    elif is_decreasing(n1, n2):
        last_n = n2
        for n in list[2:]:
            if not (is_decreasing(last_n, int(n))):
                if bad_level:
                    return True
                else:
                    bad_level = True
            else:
                last_n = int(n)
    else:
        return True
    return False

file = open("day2.csv", "r")
unsafe = 0
lines = file.read().splitlines()
for line in lines:
    list = line.split(" ")
    bad_level = False
    if is_unsafe(list, False) and is_unsafe(list[1:], True) and is_unsafe([list[0]] + list[2:], True):
        unsafe += 1
print(len(lines) - unsafe)