Day 2 — Python numbers and arithmetic

Python is a very good calculator. Today you learn every operator you will need for data work.

The operators

Notice the last one 10 / 3 gives 3.3333333333333335, and even 4 / 2 gives 2.0, not 2. In Python 3, a single slash always produces a decimal.

Floor division and remainder

% is far more useful than it looks — it is how you test whether a number divides evenly.

Powers

Order of operations

Same rules as school maths: brackets, then powers, then × and ÷, then + and −.

Updating a variable

+= means "add this to what is already there". You will use it constantly in loops.

A real calculation

round()

Money should almost never be printed with 12 decimal places.

Try these yourself

Work out 15% of 82000.
Check whether 4567 is even using %.
Calculate the average of 42000, 38500 and 51200.
Round 3.14159 to 3 decimal places.

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