Value error due to improper storing of float value

Question

Computers can't store floats perfectly accurately, in the same way that we can't write down the complete decimal expansion of 1/3 (0.3333333333333333...). Keep this in mind, because it often leads to infuriating bugs!

How do we avoid above bugs and how to find the accurate decimal value.

eg:
length = int(input("Enter Length:"))
diameter = int(input("Enter Diameter:"))
Total_Volume = int(input("Enter Total volume:"))
Radius = diameter/2
r=round(Radius,1)
Volume_1_cargo = (1.3333)*3.14*(r**3)
Volume_cargo = round(Volume_1_cargo,2)
volume_container = length**3
total_volume_spent = Volume_cargo*Total_Volume
remaining_volume = volume_container-total_volume_spent
print ("{0:.2f}".format(remaining_volume))

For above code my result should be : 4981.58
But am getting 4981.54

Enter Length:18
Enter Diameter:5
Enter Total volume:13
4981.54

Kindly help how to overcome these sort of issues

Answer 1

There is no fix for that, it's an error related to how numbers are represented, for example:
0.1+0.1+0.1=0.3000000000004
what you can do is try to multiply the values, then divide them again, for example:
(0.1*10+0.1*10+0.1*10)/10=0.3
So you have to think of a formula that will leave your number big enought to be divided accuratly, then divide the big result again
But it's really difficult to try and fix it, for example:
0.3 = 0.3, but 0.3+5-5 =0.29999999999998

Answer 2

A difference of 0.04 is quite insignificant, but if you want to get 4981.58 as the result, don't round the value of "Volume_1_cargo".

Volume_cargo = Volume_1_cargo