From c019dff618459d238ccd5396e9d05f81d8bbd532 Mon Sep 17 00:00:00 2001
From: francium <francium@francium.cc>
Date: Mon, 29 Jan 2024 22:05:00 -0500
Subject: [PATCH] docs: update readme to mention usage of isinstance to narrow
 types

---
 README.md | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/README.md b/README.md
index fe75a84..0c377ae 100644
--- a/README.md
+++ b/README.md
@@ -156,6 +156,27 @@ False
 True
 ```
 
+The benefit of `isinstance` is better type checking that type guards currently
+do not offer,
+
+```python
+res1: Result[int, str] = some_result()
+if isinstance(res1, Err):
+    print("Error...:", res1.err_value) # res1 is narrowed to an Err
+    return
+res1.ok()
+
+res2: Result[int, str] = some_result()
+if res1.is_err():
+    print("Error...:", res2.err_value) # res1 is NOT narrowed to an Err here
+    return
+res1.ok()
+```
+
+There is a proposed [PEP 724 – Stricter Type Guards](https://peps.python.org/pep-0724/)
+which may allow the `is_ok` and `is_err` type guards to work as expected in
+future versions of Python.
+
 Convert a `Result` to the value or `None`:
 
 ``` python