Made it I guess. Missing type hinting for frame.

.gitignore

@@ -0,0 +1,154 @@
+
+# Created by https://www.toptal.com/developers/gitignore/api/python
+# Edit at https://www.toptal.com/developers/gitignore?templates=python
+
+### Python ###
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+parts/
+sdist/
+var/
+wheels/
+pip-wheel-metadata/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+pytestdebug.log
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+doc/_build/
+
+# PyBuilder
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+.python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# poetry
+#poetry.lock
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+# .env
+.env/
+.venv/
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+pythonenv*
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# operating system-related files
+# file properties cache/storage on macOS
+*.DS_Store
+# thumbnail cache on Windows
+Thumbs.db
+
+# profiling data
+.prof
+
+
+# End of https://www.toptal.com/developers/gitignore/api/python

ProofOfConcept/const.py

@@ -1,30 +0,0 @@
-import sys
-from dataclasses import dataclass
-from typing import Any
-from IPython import embed
-
-@dataclass
-class ConstVar:
-    frame: Any # too lazy to type hint correctly. Doesn't matter
-    name: str
-    value: Any
-
-ConstList= []
-
-def checkConsts(*a):
-    for cvar in ConstList:
-        if cvar.frame.f_locals[cvar.name] != cvar.value:
-            cvar.frame.f_locals[cvar.name] = cvar.value
-            raise SyntaxError('Cannot assign value to constant')
-
-class ConstSetter:
-    def __setattr__(self, key, value):
-        target_frame = sys._getframe(1)
-        target_frame.f_locals[key] = value
-        target_frame.f_trace = checkConsts
-        target_frame.f_trace_opcodes = True
-        target_frame.f_trace_lines = False
-        ConstList.append(ConstVar(target_frame, key, value))
-
-const = ConstSetter()
-sys.settrace(lambda *a: None)

ProofOfConcept/runme.py

@@ -1,8 +0,0 @@
-from const import const
-
-# Create a new constant
-const .a = 5
-print(a)
-
-# Let's try to assign something to it
-a = 6

pyconstants.py

@@ -0,0 +1,33 @@
+import sys
+from collections import defaultdict
+from typing import Dict, Callable, List, Final
+from dataclasses import dataclass
+
+FRAMETYPE = object
+
+@dataclass
+class ConstantValue:
+    frame: FRAMETYPE # FIXME
+    name: str
+    value: object
+
+def _traceFun(frame: FRAMETYPE, event: str, arg: object) -> None: # FIXME
+    for constant in constMap[frame]:
+        if constant.name in frame.f_locals and frame.f_locals[constant.name] != constant.value:
+            frame.f_locals[constant.name] = constant.value 
+            raise SyntaxError(f"Cannot assign value to constant {repr(constant.name)}")
+
+class _ConstClass:
+    def __setattr__(self, name, value):
+        """This is the method called when a new constant is created"""
+        targetFrame = sys._getframe(1)
+        targetFrame.f_trace_lines = False
+        targetFrame.f_trace_opcodes = True
+        targetFrame.f_trace = _traceFun 
+        targetFrame.f_locals[name] = value
+        constMap[targetFrame].append(ConstantValue(targetFrame, name, value))
+
+
+constMap: Dict[FRAMETYPE, List[ConstantValue]] = defaultdict(list) # FIXME
+sys.settrace(lambda frame, event, arg: None)
+const = _ConstClass()

test.py

@@ -0,0 +1,9 @@
+import pytest
+from pyconstants import const
+
+def test_costant():
+    # It's not that complex, why am I even writing tests?
+    const .myvar = 5
+    with pytest.raises(SyntaxError):
+        myvar = 7
+    assert myvar == 5