Python: OOP design for event pricing updates
After a small check, it seems the best solution is to add a condition per type of event, where you adjust accordingly.

Since all events have their effect 'doubled' on the last 7 days, you can use a single if for it

Lastly, you use a single if as well to check if you can update the event, regarding final price

Also I added a list comprehension to avoid looping through 'construction' events, whose value never changes

class EventPricingUpdate(object):
    ORIGINAL_REDUCTION = 10

    def __init__(self, events):
        self.events = events

    def events_to_update(self):
        return [event for event in self.events if event.event_type != 'construction']

    def update(self):
        for event in self.events_to_update():
            reduction = self.ORIGINAL_REDUCTION

            if event.event_type == 'music':
                reduction = reduction * -1

            if event.event_type == 'sports':
                reduction = reduction * 2

            if event.days_from_start &lt; 7:
                reduction = reduction * 2

            # if you use python 2 this if needs a slight change
            if 500 &gt;= event.price - reduction &gt;= 50:
                event.price -= reduction

            event.days_from_start -= 1

        return self.events


# Fill some events
events = [
    Event(event_type='construction', days_from_start=10, price=100),
    Event(event_type='music', days_from_start=10, price=100),
    Event(event_type='sports', days_from_start=10, price=100)
]

EventPricingUpdate(events).update()

# Check update
assert events[0].price == 100
assert events[1].price == 110
assert events[2].price == 80


As you can see, is easy to plug new events, just a new condition on the loop

If you want to go further on the refactoring, you will add the reduction on the list comprehension method