Add classes_and_objects_exercise1.py: demonstrate mypy type checking

- Create Person class with type-annotated __init__ method
- Add name (str), age (int), and preferred_operating_system (str) attributes
- Create example instances (imran and eliza)
- Intentionally access undefined 'address' attribute to demonstrate mypy error detection
- Document the mypy error and explain the missing attribute issue

Author: Iswanna

prep/classes_and_objects_exercise1.py

@@ -0,0 +1,17 @@
+class Person:
+    def __init__(self, name: str, age: int, preferred_operating_system: str):
+        self.name = name
+        self.age = age
+        self.preferred_operating_system = preferred_operating_system
+
+imran = Person("Imran", 22, "Ubuntu")
+print(imran.name)
+print(imran.address)
+
+eliza = Person("Eliza", 34, "Arch Linux")
+print(eliza.name)
+print(eliza.address)
+
+# Answer
+# The error returned after running mypy classes_and_objects_exercise1.py means that the Person class does not have an address attribute.
+# An instance of Person was created with name, age and preferred_operating_system only.