Merge pull request #371 from realpython/3-12-error-messages

Add materials for 3.12 error messages tutorial

Author: KateFinegan

python-312/README.md

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+# Python 3.12 Demos
+
+This repository holds example code that demos some of the new features in Python 3.12.
+
+## Introduction
+
+You need Python 3.12 installed to run these examples. See the following tutorial instructions:
+
+- [How Can You Install a Pre-Release Version of Python](https://realpython.com/python-pre-release/)
+
+You can learn more about Python 3.12's new features in the following Real Python tutorials:
+
+- [Python 3.12 Preview: Ever Better Error Messages](https://realpython.com/python312-error-messages/)
+
+You'll find examples from all these tutorials in this repository.
+
+## Examples
+
+This section only contains brief instructions on how you can run the examples. See the tutorials for technical details.
+
+### Improved Error Messages
+
+Run [`encoder.py](encoder.py) to create an encoded message like the one shown in the tutorial. You can decode the message using [`decoder.py](decoder.py).
+
+You can swap the import statement to `import d from this` in either of the files to encounter the improved error message:
+
+```python
+>>> import d from this
+  File "<stdin>", line 1
+    import d from this
+    ^^^^^^^^^^^^^^^^^^
+SyntaxError: Did you mean to use 'from ... import ...' instead?
+```
+
+In [`local_self.py`](local_self.py), you can see a naive reproduction of another improved error message. Pick apart the example code to learn more about how this was implemented in Python 3.12. 
+
+See [Ever Better Error Messages in Python 3.12](https://realpython.com/python312-error-messages/) for more information.
+
+## Authors
+
+- **Martin Breuss**, E-mail: [[email protected]]([email protected])
+- **Bartosz Zaczyński**, E-mail: [[email protected]]([email protected])
+- **Geir Arne Hjelle**, E-mail: [[email protected]]([email protected])
+
+## License
+
+Distributed under the MIT license. See [`LICENSE`](../LICENSE) for more information.

python-312/decoder.py

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+from this import d
+
+message = "Gunaxf sbe nyy gur nqqrq pynevgl va reebe zrffntrf, Cnoyb!"
+
+decoded_characters = []
+for character in message:
+    if character.isalpha():
+        decoded_characters.append(d.get(character, ""))
+    else:
+        decoded_characters.append(character)
+decoded_message = "".join(decoded_characters)
+
+print(decoded_message)

python-312/encoder.py

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+from this import d
+
+message = "Thanks for all the added clarity in error messages, Pablo!"
+
+reverse_cypher_dict = {value: key for key, value in d.items()}
+
+encoded_characters = []
+for character in message:
+    if character.isalpha():
+        encoded_characters.append(reverse_cypher_dict.get(character, ""))
+    else:
+        encoded_characters.append(character)
+
+encoded_message = "".join(encoded_characters)
+
+print(encoded_message)

python-312/local_self.py

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+import inspect
+
+
+class Greeter:
+    def __init__(self):
+        self.message = "Hello"
+
+    def greet(self, whom="World"):
+        frame = inspect.currentframe()
+        wrong_name = "message"
+
+        if "self" in frame.f_locals:
+            self = frame.f_locals["self"]
+            if hasattr(self, wrong_name):
+                raise NameError(
+                    (
+                        f"name '{wrong_name}' is not defined. "
+                        f"Did you mean: 'self.{wrong_name}'?"
+                    )
+                )
+
+
+Greeter().greet()