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   3 - gt   3  3  - gt   3  3 0 - gt   3  3 1 - gt   3 1  3 14 - gt   3 14  3 140 - gt   3 14

User · Answer

You can use max   like this   print max int x   x

User · Answer

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    gt  gt  gt    g    0 000035  3 5e-05    15 decimal places seems to avoid strange behavior and has plenty of precision for my needs    gt  gt  gt      15f    1 35  rstrip  0   rstrip       1 35   gt  gt  gt      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      gt  gt  gt  Decimal  0 21000000000000000000000000006   normalize   Decimal  0 2100000000000000000000000001    gt  gt  gt  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    gt  gt  gt  Decimal 1 35  Decimal  1 350000000000000088817841970012523233890533447265625    gt  gt  gt  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

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OP would like to remove superflouous zeros and make the resulting string as short as possible   I find the  g exponential formatting shortens the resulting string for very large and very small values  The problem comes for values that don t need exponential notation  like 128 0  which is neither very large or very small   Here is one way to format numbers as short strings that uses  g exponential notation only when Decimal normalize creates strings that are too long  This might not be the fastest solution  since it does use Decimal normalize    def floatToString  inputValue  precision   3       rc   str Decimal inputValue  normalize        if  E  in rc or len rc   gt  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

User · Answer

You can simply use format   to achieve this   format 3 140    10g   where 10 is the precision you want

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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 -

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You can achieve that in most pythonic way like that   python3      0 0f   format num

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For float you could use this   def format float num       return    i  if num    int num  else   s     num   Test it    gt  gt  gt  format float 1 00000   1   gt  gt  gt  format float 1 1234567890000000000   1 123456789    For Decimal see solution here  https   stackoverflow com a 42668598 5917543

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What about trying the easiest and probably most effective approach  The method normalize   removes all the rightmost trailing zeros   from decimal import Decimal  print  Decimal  0 001000   normalize      Result  0 001   Works in Python 2 and Python 3   -- Updated --  The only problem as  BobStein-VisiBone pointed out  is that numbers like 10  100  1000    will be displayed in exponential representation  This can be easily fixed using the following function instead   from decimal import Decimal   def format float f       d   Decimal str f        return d quantize Decimal 1   if d    d to integral   else d normalize

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Using the QuantiPhy package is an option  Normally QuantiPhy is used when  working with numbers with units and SI scale factors  but it has a variety of  nice number formatting options        gt  gt  gt  from quantiphy import Quantity       gt  gt  gt  cases    3 3  3 0 3 1 3 14 3 140 3 14000  split        gt  gt  gt  for case in cases             q   Quantity case             print f  case  gt 7  - gt   q p              3 - gt  3          3  - gt  3         3 0 - gt  3         3 1 - gt  3 1        3 14 - gt  3 14       3 140 - gt  3 14     3 14000 - gt  3 14   And it will not use e-notation in this situation        gt  gt  gt  cases    3 14e-9 3 14 3 14e9  split        gt  gt  gt  for case in cases             q   Quantity case             print f  case  gt 7  - gt   q  p        3 14e-9 - gt  0        3 14 - gt  3 14      3 14e9 - gt  3 140 000 000   An alternative you might prefer is to use SI scale factors  perhaps with units        gt  gt  gt  cases    3e-9 3 14e-9 3 3 14 3e9 3 14e9  split        gt  gt  gt  for case in cases             q   Quantity case   m              print f  case  gt 7  - gt   q           3e-9 - gt  3 nm     3 14e-9 - gt  3 14 nm           3 - gt  3 m        3 14 - gt  3 14 m         3e9 - gt  3 Gm      3 14e9 - gt  3 14 Gm

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gt  gt  gt  str a if a   1 else int a

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You could use  g to achieve this    g   3 140   or  with Python   2 6    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

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Here s a solution that worked for me  It s a blend of the solution by PolyMesh and use of the new  format   syntax   for num in 3  3   3 0  3 1  3 14  3 140      print   0  2f   format num  rstrip  0   rstrip         Output   3 3 3 3 1 3 14 3 14

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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   gt  gt  gt     99g    0 0000001  9 99999999999999954748111825886258685613938723690807819366455078125e-08

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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

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If you can live with 3  and 3 0 appearing as  3 0   a very simple approach that right-strips zeros from float representations   print   s  3 140     thanks  ellimilial for pointing out the exceptions

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5g   format x   I use this to format floats to trail zeros

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Handling  f and you should put        2f     where   2f     00 floats   Example   print  Price    2f    prices product   output   Price  1 50

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Here s the answer   import numpy  num1   3 1400 num2   3 000 numpy format float positional num1  3  trim  -   numpy format float positional num2  3  trim  -     output  3 14  and  3   trim  -  removes both the trailing zero s  and the decimal

[python] Formatting floats without trailing zeros

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