Question

I’m working my way through some code examples and I stumbled upon this:

endings = ['st', 'nd', 'rd'] + 17 * ['th'] + ['st', 'nd', 'rd'] + 7 * ['th']
+ ['st']

I understand that for numbers after 4 and until 20 they end in ‘th’ and I can see that we are adding 17 more items to the list, and I understand that ’17 * [‘th’] is adding ‘th’ to the list 17 times, however, I don’t understand how this works.

Can you shed some light on this?

Answer 1

17 * ['th'] generates ['th', 'th', ..., 'th'] (17 items).

In addition it’s worth noting 2 behaviours:

• That this is only really useful because the contents 'th' is immutable (unless of course you never intended to modify the ending list).
• The list object ['th'] is only created once, however it is extended by iterating over the original copy 17 times, appending each entry to the final ['th', ...] list. This in turn is merged with the surrounding endings via the + operator.

I don’t normally shed my light. Only about once every 6 months. If you see it lying about don’t tell anyone it’s mine.