Python: what is the difference between (1,2,3) and [1,2,3], and when should I use each?

Question

In many places, (1,2,3) (a tuple) and [1,2,3] (a list) can be used interchangeably.

When should I use one or the other, and why?

Answer 1

(1,2,3) is a tuple and [1,2,3] is a list. You either of the two represent sequences of numbers but note that tuples are immutable and list are mutable Python objects.