diff --git a/aoc/day07.py b/aoc/day07.py
index e47e44c..dae1e32 100644
--- a/aoc/day07.py
+++ b/aoc/day07.py
@@ -31,8 +31,7 @@ class Hand:
 
         value_amount = list(
             reversed(
-                sorted(
-                    list([v for k, v in self.cards_dict.items() if k != joker]))
+                sorted(list([v for k, v in self.cards_dict.items() if k != joker]))
             )
         )
         joker_amount = 0
@@ -73,16 +72,14 @@ class Day07(Aoc2[list[tuple[Hand, int]], list[tuple[Hand, int]]]):
     def parseinput1(self, inpt: str) -> list[tuple[Hand, int]]:
         lines = inpt.splitlines()
         return [
-            (Hand(line.split(" ")[0], "23456789TJQKA"),
-             int(line.split(" ")[1]))
+            (Hand(line.split(" ")[0], "23456789TJQKA"), int(line.split(" ")[1]))
             for line in lines
         ]
 
     def parseinput2(self, inpt: str) -> list[tuple[Hand, int]]:
         lines = inpt.splitlines()
         return [
-            (Hand(line.split(" ")[0], "J23456789TQKA", "J"), int(
-                line.split(" ")[1]))
+            (Hand(line.split(" ")[0], "J23456789TQKA", "J"), int(line.split(" ")[1]))
             for line in lines
         ]
 
diff --git a/aoc/day08.py b/aoc/day08.py
index bc5a2b7..b9caef3 100644
--- a/aoc/day08.py
+++ b/aoc/day08.py
@@ -1,4 +1,5 @@
 from __future__ import annotations
+from dataclasses import dataclass
 import itertools
 import math
 from typing import Optional
@@ -6,18 +7,23 @@ from typing import Optional
 from .aoc import Aoc2, AocSameParser
 
 
+@dataclass
 class Map:
-    def __init__(self, inpt: str) -> None:
+    directions: list[int]
+    rules: dict[str, tuple[str, str]]
+
+    @staticmethod
+    def from_input(inpt: str) -> Map:
         lines = inpt.splitlines()
 
-        self.directions: list[int] = [0 if rl == "L" else 1 for rl in lines[0]]
-
-        self.rules = {line[:3]: (line[7:10], line[12:15]) for line in lines[2:]}
+        directions: list[int] = [0 if rl == "L" else 1 for rl in lines[0]]
+        rules = {line[:3]: (line[7:10], line[12:15]) for line in lines[2:]}
+        return Map(directions, rules)
 
 
 class Day08(AocSameParser[Map], Aoc2[Map, Map]):
     def parseinput(self, inpt: str) -> Map:
-        return Map(inpt)
+        return Map.from_input(inpt)
 
     def part1(self, inpt: Map) -> int:
         current = "AAA"
@@ -25,21 +31,20 @@ class Day08(AocSameParser[Map], Aoc2[Map, Map]):
         for steps, direction in enumerate(itertools.cycle(inpt.directions)):
             if current == "ZZZ":
                 return steps
-            else:
-                current = inpt.rules[current][direction]
+            current = inpt.rules[current][direction]
         raise RuntimeError("End of the rainbow")
 
     def find_loop(self, list_of_nrs: list[int]) -> Optional[tuple[int, int]]:
-        for index in range(len(list_of_nrs)):
-            for index in range(len(list_of_nrs[index + 1 :])):
-                diff = list_of_nrs[index + 1] - list_of_nrs[index]
-                if list_of_nrs[index + 1] + diff in list_of_nrs:
-                    return list_of_nrs[index], diff
+        for index, nr in enumerate(list_of_nrs):
+            for nr2 in list_of_nrs[index + 1 :]:
+                diff = nr2 - nr
+                if nr2 + diff in list_of_nrs:
+                    return nr, diff
         return None
 
     def part2(self, inpt: Map) -> int:
         current = [node for node in inpt.rules.keys() if node.endswith("A")]
-        steps_to_z = [[] for _ in current]
+        steps_to_z: list[list[int]] = [[] for _ in current]
         loops: list[Optional[tuple[int, int]]] = [None for _ in current]
 
         for steps, direction in enumerate(itertools.cycle(inpt.directions)):
@@ -50,17 +55,14 @@ class Day08(AocSameParser[Map], Aoc2[Map, Map]):
 
             if not any(loop is None for loop in loops):
                 break
-            else:
-                current = [inpt.rules[node][direction] for node in current]
+            current = [inpt.rules[node][direction] for node in current]
 
         # Turns out, each path directly loops :/
         return math.lcm(*(loop[0] for loop in loops if loop is not None))
 
 
 def main() -> None:
-    day08 = Day08(2023, 8)
-    day08._example_code_nr1 = 1
-    day08._example_code_nr2 = -1
+    day08 = Day08(2023, 8, example_code_nr1=1, example_code_nr2=-1)
     day08.run()
 
 
diff --git a/aoc/day09.py b/aoc/day09.py
new file mode 100644
index 0000000..d5e47d1
--- /dev/null
+++ b/aoc/day09.py
@@ -0,0 +1,38 @@
+from functools import reduce
+from typing import Iterable
+
+from .aoc import Aoc2, AocParseLinesSameParser
+
+
+class Day09(AocParseLinesSameParser[list[int]], Aoc2[list[list[int]], list[list[int]]]):
+    def parseline(self, inpt: str) -> list[int]:
+        return [int(d) for d in inpt.split(" ")]
+
+    def derive(self, init: list[int]) -> list[int]:
+        return [y - x for x, y in zip(init, init[1:])]
+
+    def get_nth_value_in_deriv(self, values: list[int], n: int) -> Iterable[int]:
+        while any(values):
+            yield values[n]
+            values = self.derive(values)
+
+    def part1(self, inpt: list[list[int]]) -> int:
+        return sum(sum(self.get_nth_value_in_deriv(line, -1)) for line in inpt)
+
+    def part2(self, inpt: list[list[int]]) -> int:
+        return sum(
+            reduce(
+                lambda acc, x: x - acc,
+                reversed(list(self.get_nth_value_in_deriv(line, 0))),
+            )
+            for line in inpt
+        )
+
+
+def main() -> None:
+    day09 = Day09(2023, 9, example_code_nr2=0)
+    day09.run()
+
+
+if __name__ == "__main__":
+    main()