Using Python as a calculator

Calculating 2+2

One of the simplest uses of Python is as a simple calculator.

This also introduces us to the idea of working with numbers which is a key part of using Python for scientific applications.

Open a new Notebook and enter into a code cell

2+2

If you run this cell you should get something that looks like the screenshot below.

The cell has run (indicated by the number 1 to the left of the cell), and the “code” has produced a result, which is printed below the cell. Beneath that you get a new, empty cell for your next piece of code.

Within this course book cells that have been run are rendered as follows:

2+2
4

You can add space between the numbers to make things easier to read:

2 + 2
4

Or wrap the expression in brackets:

(2 + 2)
4

And still get the same result.

Simple arithmetic

You are not limited to adding numbers. Try entering the following expressions into code cells and executing them (running the cells.):

  • subtraction:

3 - 1

  • multiplication:

4 * 2

  • powers (e.g. 42)

4 ** 2

  • division

6 / 2

Integers and Floats

Notice that the last example gives 3.0 and not 3 as the result. Python distinguishes between integers (also called ints) and floating point numbers (also called floats):

  • Integers: A number without a decimal point: e.g. 1, 2, 100, 2100.

  • Floats: A number with a decimal point. e.g. 3.14159, 12.0107, 8.3144 (you might recognise these).

Arithmetic also works with floats:

2.0 + 2.0

4.0 * 2.0

4.0 ** 2.0

6.0 / 2.0

And with mixtures of integers and floats

2 + 2.0

4 * 2.0

4.0 ** 2

6 / 2.0

Notice how these last examples always output a float.

floats can also be written without any numbers after the decimal point, e.g.

42.

is the same as 42.0.

You can do integer division (also called floor division ) using //:

6 // 2

Integer division rounds down:

7 // 2

You can calculate the remainder of integer division using the % symbol (called the modulo operator).

7 % 2

8 % 2

Brackets can be used to specify the order of operations in more complicated expressions, according to the usual mathematical rules:

(2 + 3) * 4

2 + (3 * 4)

We will return to mathematical expressions in Python in more detail later in the course.