tuple.py

"""
Tuples are an ordered collection of values that cannot be modified at
runtime. This module shows how tuples are created, iterated, accessed
and combined.
"""


def main() -> None:
 # This is a tuple of integers
 immutable = (1, 2, 3, 4)

 # It can be indexed like a list
 assert immutable[0] == 1
 assert immutable[-1] == 4

 # It can be sliced like a list
 assert immutable[1:3] == (2, 3)
 assert immutable[3:4] == (4,)
 assert immutable[1::2] == (2, 4)
 assert immutable[::-1] == (4, 3, 2, 1)

 # It can be iterated over like a list
 for ix, number in enumerate(immutable):
 assert immutable[ix] == number

 # But its contents cannot be changed. As an alternative, we can
 # create new tuples from existing tuples
 bigger_immutable = immutable + (5, 6)
 assert bigger_immutable == (1, 2, 3, 4, 5, 6)
 smaller_immutable = immutable[0:2]
 assert smaller_immutable == (1, 2)

 # We use tuples when the number of items is consistent. An example
 # where this can help is a 2D game with X and Y coordinates. Using a
 # tuple with two numbers can ensure that the number of coordinates
 # doesn't change to one, three, four, etc.
 moved_count = 0
 pos_x, pos_y = (0, 0)
 for i in range(1, 5, 2):
 moved_count += 1
 pos_x, pos_y = (pos_x + 10 * i, pos_y + 15 * i)
 assert moved_count == 2
 assert pos_x == 40 and pos_y == 60


if __name__ == "__main__":
 main()