Formatting floats without trailing zeros

Question

How can I format a float so that it doesn\'t contain trailing zeros? In other words, I want the resulting string to be as short as possible.

For example:

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Answer 1

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;-).

Answer 2

You can achieve that in most pythonic way like that:

python3:

"{:0.0f}".format(num)

Answer 3

You could use %g to achieve this:

'%g'%(3.140)

or, for Python 2.6 or better:

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

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

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

Answer 4

While formatting is likely that most Pythonic way, here is an alternate solution using the more_itertools.rstrip tool.

import more_itertools as mit


def fmt(num, pred=None):
    iterable = str(num)
    predicate = pred if pred is not None else lambda x: x in {".", "0"}
    return "".join(mit.rstrip(iterable, predicate))

assert fmt(3) == "3"
assert fmt(3.) == "3"
assert fmt(3.0) == "3"
assert fmt(3.1) == "3.1"
assert fmt(3.14) == "3.14"
assert fmt(3.140) == "3.14"
assert fmt(3.14000) == "3.14"
assert fmt("3,0", pred=lambda x: x in set(",0")) == "3"

The number is converted to a string, which is stripped of trailing characters that satisfy a predicate. The function definition fmt is not required, but it is used here to test assertions, which all pass. Note: it works on string inputs and accepts optional predicates.

See also details on this third-party library, more_itertools.

Answer 5

Use %g with big enough width, for example '%.99g'. It will print in fixed-point notation for any reasonably big number.

EDIT: it doesn't work

>>> '%.99g' % 0.0000001
'9.99999999999999954748111825886258685613938723690807819366455078125e-08'

Answer 6

You can use max() like this:

print(max(int(x), x))