Program not entering if statement

Question

In my python program, an if statement is not being entered. I have simplified the code to the following:

x = -5
while x < 5:
    if (x == 0):
        prin         


        

Answer 1

Others have pointed out the issue with floating-point numbers being unable to represent values exactly. If you need exact decimal representation of a number, you can use the Decimal class:

from decimal import Decimal

x = Decimal(-5)
while x < 5:
    if (x == 0):
        print 0
    x += Decimal(".01")

This will print 0 as you expect.

Note the use of a string for the increment. If you used Decimal(.01) you'd have the same problem with accurate representation of 0.01, because you're converting from a floating-point number and have already lost the accuracy, so the class doesn't allow that.