Add mutable/immutable demos

Author: shorodilov

src/basics/__init__.py

@@ -0,0 +1,61 @@
+"""
+This module demonstrates the mutable nature of objects
+
+"""
+
+import logging
+from typing import Any, List, Optional
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+def change_mutable_v1(value: Any, mutable: List[Any]) -> List[Any]:
+    """This function will change mutable argument"""
+
+    mutable.append(value)
+    return mutable
+
+
+# noinspection PyDefaultArgument
+def change_mutable_v2(value: Any,
+                      mutable: Optional[List[Any]] = []) -> List[Any]:
+    """This function will change default mutable object"""
+
+    mutable.append(value)
+    return mutable
+
+
+def change_valid(value: Any,
+                 mutable: Optional[List[Any]] = None) -> List[Any]:
+    """
+    This function wouldn't change defaults,
+    but will change mutable argument.
+    """
+
+    mutable = mutable or []
+    mutable.append(value)
+
+    return mutable
+
+
+if __name__ == "__main__":
+    mutable_obj1 = []
+    change_mutable_v1(1, mutable_obj1)
+    mutable_obj1 += [2]  # [1, 2], because it was changed by "change_mutable"
+
+    logger.info(f"{mutable_obj1 = }")
+
+    mutable_obj2 = change_mutable_v2(10)  # expected: [10]
+    mutable_obj3 = change_mutable_v2(20)  # expected: [20], but [10, 20]
+
+    logger.info(f"{mutable_obj2 = }")
+    logger.info(f"{mutable_obj3 = }")
+
+    mutable_obj4 = change_valid(100)  # expected: [100]
+    mutable_obj5 = change_valid(200)  # expected: [200]
+    mutable_obj6 = change_valid(3, mutable_obj1)  # expected: [1, 2, 3]
+
+    logger.info(f"{mutable_obj4 = }")
+    logger.info(f"{mutable_obj5 = }")
+    logger.info(f"{mutable_obj6 = }")