How to print float to n decimal places including trailing 0s

Question

I need to print or convert a float number to 15 decimal place string even if the result has many trailing 0s eg   1 6 becomes 1 6000000000000000  I tried round 6 2 15  but it returns 6 2000000000000002 adding a rounding error  I also saw various people online who put the float into a string and then added trailing 0 s manually but that seems bad     What is the best way to do this

User · Answer

I guess this is essentially putting it in a string  but this avoids the rounding error   import decimal  def display x       digits   15     temp   str decimal Decimal str x     0    digits       return temp  temp find        digits   1

User · Answer

Floating point numbers lack precision to accurately represent  1 6  out to that many decimal places   The rounding errors are real   Your number is not actually 1 6   Check out  http   docs python org library decimal html

User · Answer

For Python versions in 2 6  and 3 x  You can use the str format method  Examples    gt  gt  gt  print   0  16f   format 1 6   1 6000000000000001   gt  gt  gt  print   0  15f   format 1 6   1 600000000000000   Note the 1 at the end of the first example is rounding error  it happens because exact representation of the decimal number 1 6 requires an infinite number binary digits  Since floating-point numbers have a finite number of bits  the number is rounded to a nearby  but not equal  value   For Python versions prior to 2 6  at least back to 2 0   You can use the  modulo-formatting  syntax  this works for Python 2 6 and 2 7 too     gt  gt  gt  print    16f    1 6 1 6000000000000001   gt  gt  gt  print    15f    1 6 1 600000000000000

User · Answer

The cleanest way in modern Python  gt  3 6  is to use an f-string with string formatting    gt  gt  gt  var   1 6  gt  gt  gt  f  var  15f    1 600000000000000

[python] How to print float to n decimal places including trailing 0s?

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