Let's look at the round() function, which rounds the number passed to it:

result = round(10.25, 0)  # 10.0

We passed two parameters to it:

• Number to be rounded
• Rounding accuracy

0 means that the rounding will be to an integer value. More often than not, you need to round to a whole number, not to two, three, four etc. decimal places. So the creators of the round function made the second parameter unnecessary and gave it a default value of 0 inside the function. So, you can choose to not specify the second parameter and the result will be the same:

result = round(10.25)  # 10.0

And if you need a different precision, you can pass a parameter:

# rounding to one decimal place
result = round(10.25, 1)  # 10.2

If a function in Python accepts optional arguments, they always come after the mandatory ones. There can be any number of them. It depends on the function itself, but they always go next to and at the end of the list of arguments.

The code defines data about a car trip: the distance, the fuel consumption, the fuel price and the number of passengers.

Calculate and print three values:

1. The volume of fuel in litres needed for the trip. Round it to one decimal place.
2. The total cost of the trip. Round it to two decimal places.
3. The cost of the trip for each passenger. Round it to a whole number by calling round() without the second argument.

Each value is printed on its own line.

distance ──────┐
               ├──→ fuel ──────┐
fuel_consumption ──┘           ├──→ trip_cost ──────┐
                               │                    ├──→ per_person
fuel_price ────────────────────┘                    │
                                                    │
passengers ─────────────────────────────────────────┘