Numbers are the way we deal with everything in a computer, everything else (text, graphics, sound) gets translated into numbers so that the computer can process them:

  • to make an image brighter we add a value to each pixel

  • to make audio louder we add a value to each sample

  • to make text ALL CAPS we convert each character (number) to the equivalent uppercase character (number)

So what can we do with numbers? We’ve already seen addition and subtraction:

>>> 5.0
>>> 5 + 3
>>> 5 - 3

Multiplication is only interesting because the character we use is asterisk (*) rather than x or ×.

>>> 5 * 3

Now some division:

>>> 5 / 2
>>> 5 / 2.0
>>> 5 // 2.0
>>> 5 % 2.0
>>> 5 / 3.0


If you got the result 2 from 5 / 2 then you are likely using Python 2.7 an earlier, and now obsolete, version of Python. You should still be able to complete this tutorial, but some results may be slightly different than what we show. In python2 if you divide two integer (whole) numbers with a / then you get an integer (whole) value, just as if you had used // in Python 3.


  • Do some simple math in the interpreter

  • Can you get the interpreter to produce an error message?

  • Can you figure out what the % operator is doing?

  • Can you figure out what the // operator is doing?


Making text ALL CAPS is actually a pretty involved thing to do. We used to do it by just subtracting 32 from the character-code, but that doesn’t work well for non-English languages.

The complexity is normally handled by some already-written code that knows how to do the work in any language.