Smooth the Week

A café counts its visitors every day. The numbers jump around, so the owner wants a rolling average to see the trend.

Task: write smoothed(visitors, window).

• visitors is a list of daily counts, oldest first. window is a whole number, at least 1.
• Return the rolling average over window days, as a list of floats rounded to 1 decimal place, oldest first.
• Leave out the first days where the window isn't full yet. So the list has len(visitors) - window + 1 values.
• If window is bigger than the number of days, return an empty list.