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print("%.5f" % 5.1234567890)  output is 5.12346

i am not understanding why 5 is not printed in output in precision field. after 4 the 6 is printed directly. why?

nivedita
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  • Does this answer your question? [How to format a floating number to fixed width in Python](https://stackoverflow.com/questions/8885663/how-to-format-a-floating-number-to-fixed-width-in-python) – Henry Ecker Apr 29 '21 at 02:46

3 Answers3

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You limit the number of digits in fractional part to 5 digits. When you do that it rounds the number up or down based on number after the last digit. In your case, the fifth digit of the fractional part is 5 and after that is 6. So it rounds the number 5 up.

Sereyvath
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  • Yes, it's only a coincidence that the rounded digit `6` is the same as the following digit `6`. You would get the same result with `5.123457890`. – Mark Ransom Apr 29 '21 at 03:29
0

The number you type after the dot limits the float digits after the decimal point. so your command will prints the number and the first 5 digits of his decimal part.

Yona
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0

I don't think there is anything in the math library to do this, since obviously normal people would round that number up.

But if you are really trying to round down, for whatever reason, you would need to build a function or import some other library someone else made to do it.

You can also create a function do it, for example:

import math

def round_decimals_down(number:float, decimals:int=2):
    if not isinstance(decimals, int):
        raise TypeError("A")
    elif decimals < 0:
        raise ValueError("B")
    elif decimals == 0:
        return math.floor(number)

    factor = 10 ** decimals
    return math.floor(number * factor) / factor

valueA = 5.1234567890
roundA = round_decimals_down(valueA, 5)
print(roundA)

output: 5.12345

Let me know if that is what you were trying to accomplish.

NewCoder18
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