Formatting floats without trailing zeros

Me, I'd do ('%f' % x).rstrip('0').rstrip('.') -- guarantees fixed-point formatting rather than scientific notation, etc etc. Yeah, not as slick and elegant as %g, but, it works (and I don't know how to force %g to never use scientific notation;-).

You could use %g to achieve this:

'%g'%(3.140)

or, with Python ≥ 2.6:

'{0:g}'.format(3.140)

or, with Python ≥ 3.6:

f'{3.140:g}'

From the docs for format: g causes (among other things)

insignificant trailing zeros [to be]removed from the significand, and thedecimal point is also removed if thereare no remaining digits following it.

After looking over answers to several similar questions, this seems to be the best solution for me:

def floatToString(inputValue):    return ('%.15f' % inputValue).rstrip('0').rstrip('.')

My reasoning:

%g doesn't get rid of scientific notation.

>>> '%g' % 0.000035'3.5e-05'

15 decimal places seems to avoid strange behavior and has plenty of precision for my needs.

>>> ('%.15f' % 1.35).rstrip('0').rstrip('.')'1.35'>>> ('%.16f' % 1.35).rstrip('0').rstrip('.')'1.3500000000000001'

I could have used format(inputValue, '.15f'). instead of '%.15f' % inputValue, but that is a bit slower (~30%).

I could have used Decimal(inputValue).normalize(), but this has a few issues as well. For one, it is A LOT slower (~11x). I also found that although it has pretty great precision, it still suffers from precision loss when using normalize().

>>> Decimal('0.21000000000000000000000000006').normalize()Decimal('0.2100000000000000000000000001')>>> Decimal('0.21000000000000000000000000006')Decimal('0.21000000000000000000000000006')

Most importantly, I would still be converting to Decimal from a float which can make you end up with something other than the number you put in there. I think Decimal works best when the arithmetic stays in Decimal and the Decimal is initialized with a string.

>>> Decimal(1.35)Decimal('1.350000000000000088817841970012523233890533447265625')>>> Decimal('1.35')Decimal('1.35')

I'm sure the precision issue of Decimal.normalize() can be adjusted to what is needed using context settings, but considering the already slow speed and not needing ridiculous precision and the fact that I'd still be converting from a float and losing precision anyway, I didn't think it was worth pursuing.

I'm not concerned with the possible "-0" result since -0.0 is a valid floating point number and it would probably be a rare occurrence anyway, but since you did mention you want to keep the string result as short as possible, you could always use an extra conditional at very little extra speed cost.

def floatToString(inputValue):    result = ('%.15f' % inputValue).rstrip('0').rstrip('.')    return '0' if result == '-0' else result