object size measurement function, related to #7

src/dopt_basics/system.py

@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+import sys
+from dataclasses import fields, is_dataclass
+from typing import Any, Literal
+
+
+def obj_size(
+    obj: Any,
+    seen: set[int] | None = None,
+    unit: Literal["b", "kb", "mb", "gb"] = "b",
+) -> float:
+    size = sys.getsizeof(obj)
+    if seen is None:
+        seen = set()
+
+    obj_id = id(obj)
+    if obj_id in seen:
+        return 0
+    seen.add(obj_id)
+
+    if is_dataclass(obj):
+        for f in fields(obj):
+            size += obj_size(getattr(obj, f.name), seen)
+    elif isinstance(obj, dict):
+        size += sum(obj_size(v, seen) + obj_size(k, seen) for k, v in obj.items())
+    elif isinstance(obj, (list, tuple, set)):
+        size += sum(obj_size(i, seen) for i in obj)
+
+    match unit:
+        case "kb":
+            size /= 1024
+        case "mb":
+            size /= 1024 * 1024
+        case "gb":
+            size /= 1024 * 1024 * 1024
+
+    return size