Python - Round to nearest 05

Question

Hvor can I en python do the following rounding:

Round to the nearest 05 decimal

7,97 -> 7,95

6,72 -> 6,70

31,06 -> 31,05

36,04 -> 36,

Answer 1

I faced the same problem and as I didn't find the ultimate solution to this, here's mine.

Firs of all the main part(which was answered before):

def round_to_precision(x, precision):
    # This correction required due to float errors and aims to avoid cases like:
    # 100.00501 / 0.00001 = 10000500.999999998
    # It has a downside as well - it may lead to vanishing the difference for case like
    # price = 100.5 - (correction - correction/10), precision = 1 => 101 not 100
    # 5 decimals below desired precision looks safe enough to ignore
    correction = 1e-5 if x > 0 else -1e-5
    result = round(x / precision + correction) * precision
    return round(result, find_first_meaningful_decimal(precision))

The only tricky part here was that find_first_meaningful_decimal, which I've implemented like this:

def find_first_meaningful_decimal(x):
    candidate = 0
    MAX_DECIMAL = 10
    EPSILON = 1 / 10 ** MAX_DECIMAL
    while round(x, candidate) < EPSILON:
        candidate +=1
        if candidate > MAX_DECIMAL:
            raise Exception('Number is too small: {}'.format(x))
    if int(x * 10 ** (candidate + 1)) == 5:
        candidate += 1
    return candidate


print(round_to_precision(129.950002, 0.0005))
print(round_to_precision(-129.95005, 0.0001))

129.9505
-129.9501