我如何格式化一个浮点数，使它不包含尾随零?换句话说，我希望得到的字符串尽可能短。
例如:
3 -> "3"
3. -> "3"
3.0 -> "3"
3.1 -> "3.1"
3.14 -> "3.14"
3.140 -> "3.14"
当前回答
OP希望删除多余的零，并使生成的字符串尽可能短。
我发现%g指数格式缩短了非常大和非常小的值的结果字符串。问题出现在不需要指数符号的值上，比如128.0，它既不是很大也不是很小。
这里有一种将数字格式化为短字符串的方法，仅在Decimal时使用%g指数表示法。Normalize创建的字符串太长。这可能不是最快的解决方案(因为它使用Decimal.normalize)
def floatToString (inputValue, precision = 3):
rc = str(Decimal(inputValue).normalize())
if 'E' in rc or len(rc) > 5:
rc = '{0:.{1}g}'.format(inputValue, precision)
return rc
inputs = [128.0, 32768.0, 65536, 65536 * 2, 31.5, 1.000, 10.0]
outputs = [floatToString(i) for i in inputs]
print(outputs)
# ['128', '32768', '65536', '1.31e+05', '31.5', '1', '10']
其他回答
你可以简单地使用format()来实现:
格式(3.140，'.10g')，其中10是您想要的精度。
“(5g)。”format (x)
我用这个来格式化浮点到尾零。
处理%f和你应该放
% .2f
,地点: .2f == .00浮动。
例子:
价格:%。2f" %价格[产品]
输出:
价格:1.50
一个新的挑战者出现了。
def prettify_float(real: float, precision: int = 2) -> str:
'''
Prettify the passed floating-point number into a human-readable string,
rounded and truncated to the passed number of decimal places.
This converter prettifies floating-point numbers for human consumption,
producing more readable results than the default :meth:`float.__str__`
dunder method. Notably, this converter:
* Strips all ignorable trailing zeroes and decimal points from this number
(e.g., ``3`` rather than either ``3.`` or ``3.0``).
* Rounds to the passed precision for perceptual uniformity.
Parameters
----------
real : float
Arbitrary floating-point number to be prettified.
precision : int, optional
**Precision** (i.e., number of decimal places to round to). Defaults to
a precision of 2 decimal places.
Returns
----------
str
Human-readable string prettified from this floating-point number.
Raises
----------
ValueError
If this precision is negative.
'''
# If this precision is negative, raise an exception.
if precision < 0:
raise ValueError(f'Negative precision {precision} unsupported.')
# Else, this precision is non-negative.
# String prettified from this floating-point number. In order:
# * Coerce this number into a string rounded to this precision.
# * Truncate all trailing zeroes from this string.
# * Truncate any trailing decimal place if any from this string.
result = f'{real:.{precision}f}'.rstrip('0').rstrip('.')
# If rounding this string from a small negative number (e.g., "-0.001")
# yielded the anomalous result of "-0", return "0" instead; else, return
# this result as is.
return '0' if result == '-0' else result
不要相信我的谎言
pytest风格的单元测试，否则就不会发生。
def test_prettify_float() -> None:
'''
Test usage of the :func:`prettify_float` prettifier.
'''
# Defer test-specific imports.
from pytest import raises
# Assert this function prettifies zero as expected.
assert prettify_float(0.0) == '0'
# Assert this function prettifies a negative integer as expected.
assert prettify_float(-2.0) == '-2'
# Assert this prettifier prettifies a small negative float as expected.
assert prettify_float(-0.001) == '0'
# Assert this prettifier prettifies a larger negative float as expected.
assert prettify_float(-2.718281828) == '-2.72'
assert prettify_float(-2.718281828, precision=4) == '-2.7183'
# Assert this function prettifies a positive integer as expected.
assert prettify_float(3.0) == '3'
# Assert this function prettifies a positive float as expected.
assert prettify_float(3.14159265359) == '3.14'
assert prettify_float(3.14159265359, precision=4) == '3.1416'
# Assert this prettifier raises the expected exception when passed a
# negative precision.
with raises(ValueError):
prettify_float(2.718281828, precision=-2)
%100纯Python
忽略那些诱人的简单答案，比如:
琐碎的一行。它们在常见的边缘情况下都失败了，比如整数或小的负浮点数。 第三方包。NumPy, QuantiPhy和more_itertools?你肯定是在开玩笑。不要额外增加维护负担或代码债务。也就是说……
在prettify_float()上抛出@beartype，以增加运行时安全性，你就成功了!你的用户群会对你赞不绝口。那我也是，我很确定我的偏见在这里表现出来了。
另请参阅
这个答案站在巨大的猛犸象的肩膀上，包括:
亚历克斯·马尔泰利聪明的回答。 PolyMesh对Martelli答案的推广，以捕捉小负浮的边缘情况。 Kaushal Modi对PolyMesh的答案进行了概括，以强制实现小数点后两位的精度。
你可以用最python的方式来实现:
python3:
"{:0.0f}".format(num)
