diff --git a/d00/ex04/whatis.py b/d00/ex04/whatis.py
new file mode 100644
index 0000000..ffb6ac5
--- /dev/null
+++ b/d00/ex04/whatis.py
@@ -0,0 +1,24 @@
+def check_parity(args: list[str]):
+    if len(args) == 0:
+        return
+    if len(args) > 1:
+        print("AssertionError: more than one argument is provided")
+        return
+
+    arg = args[0]
+    try:
+        number = int(arg)
+    except ValueError:
+        print("AssertionError: argument is not an integer")
+        return
+
+    if number % 2 == 0:
+        print("I'm Even.")
+    else:
+        print("I'm Odd.")
+
+# execute module as a script : https://docs.python.org/3.10/tutorial/modules.html#executing-modules-as-scripts
+if __name__ == "__main__":
+    # https://docs.python.org/3.10/library/sys.html
+    import sys
+    check_parity(sys.argv[1:])
\ No newline at end of file