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 a useless trailing zero (though not always) that I want to get rid of. For example...

from decimal import Decimal  # outputs 25.0,  PROBLEM!  I would like it to output 25 print Decimal('2.5') * 10  # outputs 2567.8000, PROBLEM!  I would like it to output 2567.8 print Decimal('2.5678') * 1000 

Is there a function that tells the decimal object to drop these insignificant zeros? The only way I can think of doing this is to convert to a string and replace them using regular expressions.

Should probably mention that I am using python 2.6.5

EDIT senderle's fine answer made me realize that I occasionally get a number like 250.0 which when normalized produces 2.5E+2. I guess in these cases I could try to sort them out and convert to a int

Answer 1

There's probably a better way of doing this, but you could use .rstrip('0').rstrip('.') to achieve the result that you want.

Using your numbers as an example:

>>> s = str(Decimal('2.5') * 10) >>> print s.rstrip('0').rstrip('.') if '.' in s else s 25 >>> s = str(Decimal('2.5678') * 1000) >>> print s.rstrip('0').rstrip('.') if '.' in s else s 2567.8 

And here's the fix for the problem that gerrit pointed out in the comments:

>>> s = str(Decimal('1500')) >>> print s.rstrip('0').rstrip('.') if '.' in s else s 1500 

Answer 2

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')