Simple Code - Strange Results?

[emerger]

Here's a simple code I ran for practice as part of my class. Below are the results. Can anyone tell me why the increment when to the ?trillionth+? decimal place and not the thousandth that I specified?

import os
import sys
import re

votes=3
while True:
    votes=votes + .001
    print(votes)
    if votes>=5:
        break

Result(portion of...)
4.9870000000002195
4.98800000000022
4.98900000000022
4.9900000000002205
4.991000000000221
4.992000000000221
4.9930000000002215
4.994000000000222
4.995000000000222
4.9960000000002225
4.997000000000223
4.998000000000223
4.9990000000002235
5.000000000000224

[Larz60+]

As soon as you add a float to an int, the int becomes a float.
Floats are made up of two values, the exponent and mantissa, so you can not expect that
floating point will be exact, but very close.

[emerger]

Understood. Thank you very much

[league55]

Floating point arithmetic is notoriously imprecise because of how computer hardware handles floating point numbers. The trillionths arise from that imprecision.

[snippsat]

Some point on round() and force decimal places {:.2f} --> 2 decimal places.

votes = 3
while True:
    votes = votes + .001
    print(round(votes, 3))
    #print('{:.2f}'.format(votes))
    if votes >= 5:
        break

To overcome it decimal,can be important in eg finance calculation.

from decimal import Decimal

votes = Decimal('3')
while True:
    votes = votes + Decimal('.001')
    print(votes)
    if votes >= 5:
        break

Output:
....
4.990
4.991
4.992
4.993
4.994
4.995
4.996
4.997
4.998
4.999
5.000

[ka06059]

i ran your code in python 2.7 it looped all the way to 5.0, each result either less or equal to number of decimal spaces you specified