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

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?

This question is related to python floating-point

The answer is


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]

The cleanest way in modern Python >=3.6, is to use an f-string with string formatting:

>>> var = 1.6
>>> f"{var:.15f}"
'1.600000000000000'

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