Merge pull request #411 from bozhodimitrov/ep584-585

Examples for episode 584 & 585

Author: asottile

sample_code/ep584/README.md

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+# [debugging flaky cascading failure after upgrading pytest!](https://youtu.be/zyZXdvJgGPM)
+
+another deep dive debugging session!  I utilize a dirty bisect to figure out what introduced the behaviour.  from there test pollution helped me find a reproduction and then I isolated what was interfering and utilized a new technique to find _why_!
+
+## Setup commands
+
+```bash
+git clone git@github.com:pytest-dev/pytest
+git clone git@github.com:getsentry/sentry
+```
+
+## Interactive examples
+
+### Python
+
+```python
+import sys
+import pytest
+
+
+@pytest.fixture(autouse=True, scope='session')
+def settrace():
+    with open(f'trace.{os.getpid()}', 'a+') as f:
+        def tracefunc(frame, event, arg):
+            if (
+                event == 'call' and
+                '/new_migrations/monkey/' not in frame.f_code.co_filename and
+                any(
+                    s in frame.f_code.co_filename
+                    for s in (
+                        '/src/sentry/testutils/', '/tests/sentry/',
+                        '/django/test/', '/pytest_django/',
+                )
+            ):
+                f.write(f'{frame.f_code.co_filename}:{frame.f_code.co_name}\n')
+
+        orig = sys.settrace(tracefunc)
+        yield
+        sys.settrace(orig)
+```
+
+### Bash
+
+Session 1:
+
+```bash
+cd pytest/
+git log --oneline --first-parent 8.1.0..8.2.0
+git log --oneline --first-parent 8.1.0..8.2.0 -- src
+```
+
+Session 2:
+
+```bash
+cd sentry/
+pytest --setup-plan tests/sentry/utils/test_math.py | less
+
+diff -u planbefore planafter | less
+jq . last-failed-list
+diff -u trace.old trace.new | less
+
+virtualenv venv
+./venv/bin/pip install pytest pytest-rerunfailures
+./venv/bin/pytest --reruns=2 -s t.py
+```

sample_code/ep584/rev01/t.py

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+from unittest import TestCase
+
+g = True
+
+
+class TestCaseTest(TestCase):
+    @classmethod
+    def tearDownClass(cls):
+        print('class teardown!')
+
+    def test(self):
+        global g
+        print('test!')
+        if g:
+            print('flaky fail!')
+            g = False
+            raise AssertionError('#')

sample_code/ep585/README.md

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+# [how does python's module `__getattr__` actually work?](https://youtu.be/K1-wYUSQoF8)
+
+today I walk you through a bit of a deep dive into how modules work, what we used to do before this feature, and where the magic lives in cpython!
+
+## Setup commands
+
+```bash
+git@github.com:python/cpython
+```
+
+## Interactive examples
+
+### Python
+
+```python
+import t
+t.foo
+
+import sys
+sys.modules
+sorted(sys.modules)
+
+class C:
+    def __getattr__(self, x):
+        print(f'looking up {x}')
+        return x * 2
+
+sys.modules['c'] = C()
+import c
+c
+c.foo
+
+src = open('/usr/lib/python3.13/typing.py').read()
+globs = {'__name__': 'typing'}
+exec(src, globs)
+
+typing = type('typing', (), globs)
+typing
+
+typing.OrderedDict
+typing.Match
+
+typing.__getattr__
+typing().Match
+
+import sys
+import os
+os
+import typing
+typing
+type(typing)
+
+import types
+types.ModuleType
+
+type(os)
+import sys
+type(sys)
+
+import _decimal
+type(_decimal)
+```
+
+### Bash
+
+```bash
+python3
+
+git clone git@github.com:asottile/flake8-typing-imports
+cd flake8-typing-imports/
+
+nano flake8_typing_imports.py
+nano bin/build-generated
+
+git log -- bin/build-generated
+git checkout <commit_hash>
+nano bin/build-generated
+
+python 3.13 -m pydoc typing
+nano /usr/lib/python3.13/typing.py
+
+python3.13
+
+cd ../cpython/
+ls Python/
+ls Objects/
+ls Modules/
+
+nano Objects/moduleobject.c
+
+cd ../flake8-typing-imports/
+git checkout main
+nano bin/build-generated
+```

sample_code/ep585/rev01/t.py

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+def __getattr__(x: str) -> object:
+    print(f'looking for {x}')
+    return x * 2