diff --git a/7/nospaceleft.py b/7/nospaceleft.py
index 1585711..2d6d92a 100644
--- a/7/nospaceleft.py
+++ b/7/nospaceleft.py
@@ -1,24 +1,24 @@
-from collections import defaultdict
-
 from aocd.models import Puzzle
 from aocd import submit
 
+
 def get_sizes_a(dirs: dict, max_size: int) -> int:
     """
     return the size of all dirs which are at most max_size big
     """
-    filtered_dirs = [ value for value in dirs.values() if value < max_size]
+    filtered_dirs = [value for value in dirs.values() if value < max_size]
     return sum(filtered_dirs)
 
+
 def get_sizes_b(dirs: dict, needed_size: int) -> int:
     """
     return the smallest size of a dir which when deleted amounts
     to the needed size of 30M.
     """
     total_size = 70000000
-    used_size = dirs[('/',)]
+    used_size = dirs[("/",)]
     max_free = needed_size - (total_size - used_size)
-    filtered_dirs = [ value for value in dirs.values() if value > max_free]
+    filtered_dirs = [value for value in dirs.values() if value > max_free]
     return min(filtered_dirs)
 
 
@@ -34,25 +34,27 @@ def parse_input(input_str: str) -> list:
     available information in the following dictionary.
     - {list['/','dir','path']:int(size_sum)}
     """
-    path = []
-    dirs = defaultdict(int)
+    path = list()
+    dirs = dict()
     for line in input_str.splitlines():
         match line.split():
-            case ('$', 'cd', '..'):
+            case ("$", "cd", ".."):
                 path.pop()
-            case ('$', 'cd', name):
+            case ("$", "cd", name):
                 path.append(name)
-            case ('$', 'ls'):
+            case ("$", "ls"):
                 continue
-            case ('dir', _):
+            case ("dir", _):
                 continue
             case (size, file):
                 size = int(size)
                 for i in range(len(path)):
-                    key = tuple(path[:i+1]) # list not hashable
-                    dirs[key] += size
+                    key = tuple(path[: i + 1])  # list not hashable
+                    dirs.setdefault(key, 0)  # initialize key for += to work
+                    dirs[key] += size  # dirs needs to be initialized
     return dirs
 
+
 if __name__ == "__main__":
     # get puzzle and parse data
     puzzle = Puzzle(year=2022, day=7)