在 python 中将小分数（如 2.234556440301284e-100）舍入为 2.23e-100

Question

I'm trying to print a very small p-value to a plot (p-value = 4.3289045262877305e-11) . I need to round it to have fewer digits after the decimal so it will fit (4.33e-11) but when I'm using round(,3) it returns 0.0 . How can I return the number like this 4.33e-11 ?

Answer 1

When you use round you are changing the value and in your example rounding to the nearest thousandth. You only want to change the display format. "{:.2e}".format(4.3289045262877305e-11) will create a string with the representation you want. 4.33e-11

More details: https://kite.com/python/answers/how-to-print-a-number-in-scientific-notation-in-python

Answer 2

When using round(,3) you are rounding up the actual value to 0,00 , not the displayed value. If you actually need to round the value itself and not the displayed one, I would suggest you to multiply it by e11 , then round (,3) , then devide it by e11 to get the rounded number.