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 ## Python How-To Examples
-by Chaiyawut Thengket
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+by Chaiyawut Thengket
+
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diff --git a/self-referencing-hints.md b/self-referencing-hints.md
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+## Self-Referencing Type Hints
+
+Inside of a class, if you write a type hint that refers to the same class Python will raise an Error because the class is not known yet.   
+For example:
+```python
+class Money:
+    def __add__(self, other: Money) -> Money:  # ERROR: Money is unknown
+        """Return the sum of two money objects."""
+        ... (code omitted)
+```
+
+to fix this, add the following import:
+```python
+from __future__ import annotations
+
+class Money:
+    def __add__(self, other: Money) -> Money:  # OK!
+```
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