drop trailing zeros from decimal

Question

I have a long list of Decimals and that I have to adjust by factors of 10, 100, 1000,..... 1000000 depending on certain conditions. When I multiply them there is sometimes

Answer 1

You can use the normalize method to remove extra precision.

>>> print decimal.Decimal('5.500')
5.500
>>> print decimal.Decimal('5.500').normalize()
5.5

To avoid stripping zeros to the left of the decimal point, you could do this:

def normalize_fraction(d):
    normalized = d.normalize()
    sign, digits, exponent = normalized.as_tuple()
    if exponent > 0:
        return decimal.Decimal((sign, digits + (0,) * exponent, 0))
    else:
        return normalized

Or more compactly, using quantize as suggested by user7116:

def normalize_fraction(d):
    normalized = d.normalize()
    sign, digit, exponent = normalized.as_tuple()
    return normalized if exponent <= 0 else normalized.quantize(1)

You could also use to_integral() as shown here but I think using as_tuple this way is more self-documenting.

I tested these both against a few cases; please leave a comment if you find something that doesn't work.

>>> normalize_fraction(decimal.Decimal('55.5'))
Decimal('55.5')
>>> normalize_fraction(decimal.Decimal('55.500'))
Decimal('55.5')
>>> normalize_fraction(decimal.Decimal('55500'))
Decimal('55500')
>>> normalize_fraction(decimal.Decimal('555E2'))
Decimal('55500')

Answer 2

Why not use modules 10 from a multiple of 10 to check if there is remainder? No remainder means you can force int()

if (x * 10) % 10 == 0:
    x = int(x)

x = 2/1
Output: 2

x = 3/2
Output: 1.5

Answer 3

I ended up doing this:

import decimal

def dropzeros(number):
    mynum = decimal.Decimal(number).normalize()
    # e.g 22000 --> Decimal('2.2E+4')
    return mynum.__trunc__() if not mynum % 1 else float(mynum)

print dropzeros(22000.000)
22000
print dropzeros(2567.8000)
2567.8

note: casting the return value as a string will limit you to 12 significant digits