问题
I want to format a list of floating-point numbers with at most, say, 2 decimal places. But, I don\'t want trailing zeros, and I don\'t want trailing decimal points.
So, for example, 4.001 => 4, 4.797 => 4.8, 8.992 => 8.99, 13.577 => 13.58.
The simple solution is (\'%.2f\' % f).rstrip(\'.0\')(\'%.2f\' % f).rstrip(\'0\').rstrip(\'.\'). But, that looks rather ugly and seems fragile. Any nicer solutions, maybe with some magical format flags?
回答1:
You need to separate the 0 and the . stripping; that way you won't ever strip away the natural 0.
Alternatively, use the format() function, but that really comes down to the same thing:
format(f, '.2f').rstrip('0').rstrip('.')
Some tests:
>>> def formatted(f): return format(f, '.2f').rstrip('0').rstrip('.')
...
>>> formatted(0.0)
'0'
>>> formatted(4.797)
'4.8'
>>> formatted(4.001)
'4'
>>> formatted(13.577)
'13.58'
>>> formatted(0.000000000000000000001)
'0'
>>> formatted(10000000000)
'10000000000'
回答2:
The g formatter limits the output to n significant digits, dropping trailing zeroes:
>>> "{:.3g}".format(1.234)
'1.23'
>>> "{:.3g}".format(1.2)
'1.2'
>>> "{:.3g}".format(1)
'1'
回答3:
In general working with String[s] can be slow. However, this is another solution:
>>> from decimal import Decimal
>>> precision = Decimal('.00')
>>> Decimal('4.001').quantize(precision).normalize()
Decimal('4')
>>> Decimal('4.797').quantize(precision).normalize()
Decimal('4.8')
>>> Decimal('8.992').quantize(precision).normalize()
Decimal('8.99')
>>> Decimal('13.577').quantize(precision).normalize()
Decimal('13.58')
You may find more info here: http://docs.python.org/2/library/decimal.html
来源：https://stackoverflow.com/questions/14997799/most-pythonic-way-to-print-at-most-some-number-of-decimal-places