Format python decimal as [-.0-9]*, no trailing zeros, value-preserving

Question

I'm looking for a method which takes a decimal.Decimal object x and returns a string s, such that:

x == Decimal(s)
re.match("^-?(0|[1-9][0-9]*)(.[0-9]*[1-9])?$", s) is not None
s != '-0'

In other words, the method doesn't change the value of the Decimal object; it returns a string representation which is never in scientific notation (e.g. 1e80), and never has any trailing zeros.

I would assume there is a standard library function which lets me do that, but I haven't found any. Do you know of any?

possible duplicate of [drop trailing zeros from decimal](http://stackoverflow.com/questions/11227620/drop-trailing-zeros-from-decimal) — Antti Haapala -- Слава Україні, Aug 18 '13 at 11:42
The dupee suggests two solutions, `x.normalize()` and `str(x).rstrip('0').rstrip('.')`; they both fail. ### `str(Decimal('1e-20')).rstrip('0').rstrip('.')` is `'1e-2'`, and `Decimal('1e-2') != Decimal('1e-20')`, violating the equality condition. ### `Decimal('10').normalize()` is `'1E+1'`, which violates the regex condition. ### Using `'{:f}'.format(x)` seems to work, though. — Jonas Kölker, Aug 18 '13 at 12:03
But the question is exactly the same, even though the answer is wrong — Antti Haapala -- Слава Україні, Aug 18 '13 at 12:38

Blender · Answer 1 · 2013-08-18T12:11:34.790

1

n.normalize() truncates decimals with more than 28 digits of precision, but you can use string formatting and a manual check for negative zero:

'{:f}'.format(abs(n) if n.is_zero() else n)

edited Aug 18 '13 at 12:11

answered Aug 18 '13 at 11:49

Blender

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Format python decimal as [-.0-9]*, no trailing zeros, value-preserving

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