Solution to problem 3 part 1 in Python

src/Year_2015/P3.py

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+# --- Day 3: Perfectly Spherical Houses in a Vacuum ---
+
+# Santa is delivering presents to an infinite two-dimensional grid of houses.
+
+# He begins by delivering a present to the house at his starting location, and
+# then an elf at the North Pole calls him via radio and tells him where to move
+# next. Moves are always exactly one house to the north (^), south (v), east
+# (>), or west (<). After each move, he delivers another present to the house
+# at his new location.
+
+# However, the elf back at the north pole has had a little too much eggnog, and
+# so his directions are a little off, and Santa ends up visiting some houses
+# more than once. How many houses receive at least one present?
+
+# For example:
+
+#     > delivers presents to 2 houses: one at the starting location, and one to
+# the east.
+#     ^>v< delivers presents to 4 houses in a square, including twice to the
+# house at his starting/ending location.
+#     ^v^v^v^v^v delivers a bunch of presents to some very lucky children at
+# only 2 houses.
+
+from typing import Tuple
+
+with open("files/P3.txt") as f:
+    moves = [line for line in f.read().strip().split()][0]
+
+
+def move_up(pos: Tuple[int, int]) -> Tuple[int, int]:
+    return pos[0], pos[1] + 1
+
+
+def move_down(pos: Tuple[int, int]) -> Tuple[int, int]:
+    return pos[0], pos[1] - 1
+
+
+def move_left(pos: Tuple[int, int]) -> Tuple[int, int]:
+    return pos[0] - 1, pos[1]
+
+
+def move_right(pos: Tuple[int, int]) -> Tuple[int, int]:
+    return pos[0] + 1, pos[1]
+
+
+def part_1() -> None:
+    pos = [(0, 0)]
+    for move in moves:
+        if move == "^":
+            pos.append(move_up(pos[-1]))
+        elif move == "v":
+            pos.append(move_down(pos[-1]))
+        elif move == "<":
+            pos.append(move_left(pos[-1]))
+        elif move == ">":
+            pos.append(move_right(pos[-1]))
+
+    print(f"{len(set(pos))} houses receive at least one present")
+
+
+if __name__ == "__main__":
+    part_1()