Included optional arguments

content/blog/pydataclass.md

@@ -13,7 +13,7 @@ from dataclasses import dataclass
 @dataclass
 class Person:
     name: str
-    age: int
+    age: int = 0
 ```
 
 Usage:
@@ -27,3 +27,5 @@ print(p)
 Person(name='Bob', age=20)
 ```
 
+To make an attribute have a default value, add it after the type declaration like I have with `age`.
+