Remember learning to round in grade school? Me too! The only problem is I don\u2019t use the idea very often. As a result, I don\u2019t always remember how to round a number in programming contexts like Python. Luckily, I\u2019ve pieced together a little article for myself. Hopefully, you get some value out of it as well.<\/p>\n\n\n\n
As it turns out, there are a ton of ways to a round a number in Python. For instance, we could truncate the fraction altogether using a cast to int: Rounding is one of those operations we sort of take for granted in everyday life. For instance, I use Acorns which rounds up my purchases to the nearest whole dollar and invests the excess on my behalf.<\/p>\n\n\n\n Unfortunately, rounding to whole numbers isn\u2019t an obvious operation in programming. There\u2019s no operator for rounding in most languages, and I doubt there ever will be. Instead, we often have to lean on a library or roll own one.<\/p>\n\n\n\n To make things more complicated, rounding isn\u2019t always an obvious operation. For example, how do we know when to round up or down? The way I was taught in school was to round numbers up (away from zero) when the decimal is .5 or greater.<\/p>\n\n\n\n As it turns out, there are a lot of different ways to round a whole number. In fact, I found this interesting article in the Electronic Engineering Times which outlines several different rounding methods<\/a>. To summarize, here are a few options:<\/p>\n\n\n\n Clearly, there are a lot of ways to round numbers. For the purposes of this article, we\u2019ll be using the \u201cround-half-up\u201d method. In other words, numbers like 3.5, 5.5, and -2.5 will all round up to 4, 6, and -3, respectively.<\/p>\n\n\n\n In this article, we\u2019ll take a look at a few different ways of rounding numbers in Python. As always, we\u2019ll start with the straightforward or brute force solutions. Then, we\u2019ll move our way through more common solutions.<\/p>\n\n\n\n One way to round a number is to trim the decimal place off through truncation:<\/p>\n\n\n\nint()<\/code>. Of course, there are more sophisticated options like the round()<\/code> function which rounds to the nearest even number for midway values like 7.5. That said, feel free to roll your own solution. I built my own \u201cround-half-up\u201d solution using the ternary operator: int(x + .5) if x >= 0 else int(x - .5)<\/code>. Check out the rest of the article for details. <\/p>\n\n\n\nProblem Description<\/h2>\n\n\n\n
Solutions<\/h2>\n\n\n\n
Rounding by Truncation<\/h3>\n\n\n\n