Round variable in Python 3.x

Question

I have an application that generates these values:

[ -2.00000000e+00 -1.00000000e+00 -1.00929366e-16 1.00000000e+00]

How can I round the number -1.00929366e-16 to 0 ? what I want is if there is an x number of zeros from the right point, it substituted that value with zero.

Answer 1

The simplest solution is just using the built in mathematical function

round(float)

Which will return the integer component of the float if the 10ths decimal place is less than 5 and will return one more than that if the 10ths decimal place is greater than or equal to 5.

This should be all that you require instead of counting zeros.

*Note: Since you appear to have a list of values, use

[round(each_number) for each_number in list_of_floats]

to apply the rounding to each of the values.

**Note if you are going to be applying any mathematical operations to these numbers which require any measurement of variance, I would recommend that you do not round them as you usually want to avoid having an output of 0 from calculating, say, the standard deviation if you're going to be using it in a later function (This has caused me many headaches and required me to actually include minor variation in my floats to avoid errors in later calculations).

For more information see: https://docs.python.org/3/library/functions.html#round

(Recommended by Deja Vu)

Answer 2

Correct me if I'm wrong: you don't just want to round the value. You want to do so only if "there is a number of zeroes from the right point".

Let's say this number is 5. You don't want to round 0.001 , but you want to round 0.000001 to 0. And 1.000001 to 1. Well, you can do so by checking the distance between your number and the nearest integer, like this:

def round_special(n):
    return round(n) if abs(n-round(n)) < 1e-5 else n

print round_special(0.001)
print round_special(0.0001)
print round_special(0.00001)
print round_special(0.000001)
print round_special(1.0000099)

print map(round_special, [0.001, 0.0001, 0.00001, 0.000001, 1.0000099])

Which yields:

0.001
0.0001
1e-05
0.0
1.0
[0.001, 0.0001, 1e-05, 0.0, 1.0]