Python Development Skill

Reference data for the Developer Hub, Python Specialist, and wxPython Specialist agents.

Python Version Quick Reference

Version	Key Features	EOL
3.10	`match/case` , `X \| Y` unions, `ParamSpec`	Oct 2026
3.11	Exception groups, `Self` type, `tomllib` , faster CPython	Oct 2027
3.12	Type parameter syntax `def f[T]()` , `@override` , f-string nesting	Oct 2028
3.13	Experimental free-threaded mode, improved error messages	Oct 2029
3.14	`async pdb.set_trace_async()` , template strings (PEP 750)	Oct 2030

pyproject.toml Skeleton

toml

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

[project]
name = "my-app"
version = "1.0.0"
requires-python = ">=3.10"
dependencies = []

[project.optional-dependencies]
dev = ["pytest>=8.0", "ruff>=0.6", "mypy>=1.11"]

[project.scripts]
myapp = "my_app.__main__:main"

[tool.pytest.ini_options]
testpaths = ["tests"]
addopts = "-ra --strict-markers"

[tool.ruff]
target-version = "py310"
line-length = 100

[tool.ruff.lint]
select = ["E", "F", "W", "I", "N", "UP", "B", "SIM", "TCH"]

[tool.mypy]
python_version = "3.10"
strict = true

PyInstaller Quick Reference

One-File Mode

python

exe = EXE(pyz, a.scripts, a.binaries, a.zipfiles, a.datas,
          name='MyApp', console=False, icon='icon.ico')

One-Folder Mode

python

exe = EXE(pyz, a.scripts, exclude_binaries=True,
          name='MyApp', console=False, icon='icon.ico')
coll = COLLECT(exe, a.binaries, a.zipfiles, a.datas, name='MyApp')

Common Hidden Imports

```
pkg_resources.extern
```
```
accessible_output2
```
(for a11y desktop apps)
```
keyring.backends
```
(for credential storage)
```
platformdirs
```
```
httpx._transports
```
/
```
httpcore._backends
```
```
encodings
```
(always needed)

wxPython Quick Reference

Sizer Cheat Sheet

Sizer	When to Use
`wx.BoxSizer(wx.VERTICAL)`	Stack items top-to-bottom
`wx.BoxSizer(wx.HORIZONTAL)`	Lay items left-to-right
`wx.GridBagSizer(vgap, hgap)`	Form layouts with labels + controls
`wx.FlexGridSizer(rows, cols, vgap, hgap)`	Even grid layouts
`wx.WrapSizer`	Flow layout that wraps
`wx.StaticBoxSizer(wx.VERTICAL, parent, "Label")`	Grouped controls with border

Thread-Safe GUI Updates

python

# From worker thread:
wx.CallAfter(self.update_status, "Done")
wx.PostEvent(self, CustomEvent(data=result))

# NEVER do this from a worker thread:
self.status_bar.SetStatusText("Done")  # CRASH or CORRUPTION

Standard IDs

ID	Purpose
`wx.ID_OK`	OK button
`wx.ID_CANCEL`	Cancel button
`wx.ID_SAVE`	Save action
`wx.ID_OPEN`	Open action
`wx.ID_EXIT`	Exit / Quit
`wx.ID_HELP`	Help action
`wx.ID_NEW`	New document
`wx.ID_UNDO` / `wx.ID_REDO`	Undo / Redo

Event Types

Event	Trigger
`wx.EVT_BUTTON`	Button click
`wx.EVT_MENU`	Menu item selected
`wx.EVT_CLOSE`	Window close requested
`wx.EVT_SIZE`	Window resized
`wx.EVT_TIMER`	Timer fired
`wx.EVT_TEXT`	Text control content changed
`wx.EVT_LIST_ITEM_SELECTED`	List item selected
`wx.EVT_TREE_SEL_CHANGED`	Tree selection changed
`wx.EVT_UPDATE_UI`	UI state update check

Common Pitfalls

Python

Mutable default arguments:
```
def f(items=[])
```
shares the list across calls. Use
```
None
```
and create inside.
Late binding closures:
```
lambda: x
```
in a loop captures the variable, not the value. Use
```
lambda x=x: x
```
.
Circular imports: Move imports inside functions, use
```
TYPE_CHECKING
```
block, or restructure modules.
field()
outside dataclass:
```
field()
```
is only valid inside
```
@dataclass
```
classes. Use plain type annotations elsewhere.
is
vs
==
:
```
is
```
checks identity,
```
==
```
checks equality. Use
```
is
```
only for
```
None
```
,
```
True
```
,
```
False
```
.
String concatenation in loops: Use
```
"".join()
```
or
```
io.StringIO
```
instead.

wxPython

GUI from worker thread: Always use
```
wx.CallAfter()
```
or
```
wx.PostEvent()
```
.
Missing
event.Skip()
: Other handlers won't fire. Call
```
event.Skip()
```
unless you intentionally consume the event.
Timer not stopped: Stop timers in
```
EVT_CLOSE
```
handler to prevent callbacks after destruction.
AUI not uninitialized: Call
```
_mgr.UnInit()
```
in close handler.
Dialog not destroyed: Use context managers (
```
with MyDialog(...) as dlg:
```
) for automatic cleanup.
Wrong parent for sizer items: All controls in a sizer must have the same parent panel.
Absolute positioning: Never use
```
SetPosition()
```
or
```
SetSize()
```
for layout. Always use sizers.

Cross-Platform Paths

python

from platformdirs import user_config_dir, user_data_dir, user_cache_dir

config = user_config_dir("MyApp", "MyCompany")  # %APPDATA% / ~/Library/... / ~/.config/
data = user_data_dir("MyApp", "MyCompany")
cache = user_cache_dir("MyApp", "MyCompany")

Testing Quick Reference

bash

# Run all tests
pytest

# Run specific test file
pytest tests/test_queue.py

# Run specific test
pytest tests/test_queue.py::test_submit_job -v

# With coverage
pytest --cov=mypackage --cov-report=term-missing

# Stop on first failure
pytest -x

# Show locals on failure
pytest -l

Logging Setup Template

python

import logging

def setup_logging(level: int = logging.INFO) -> None:
    logging.basicConfig(
        level=level,
        format="%(asctime)s %(name)s %(levelname)s %(message)s",
        datefmt="%Y-%m-%d %H:%M:%S",
    )
    # Quiet noisy libraries
    logging.getLogger("httpx").setLevel(logging.WARNING)
    logging.getLogger("httpcore").setLevel(logging.WARNING)

Desktop Accessibility Quick Reference

Platform API Summary

Platform	API	Python Binding
Windows	UI Automation	`comtypes` + `UIAutomationCore`
Windows	MSAA/IAccessible2	`pyia2` , `comtypes`
macOS	NSAccessibility	`pyobjc-framework-Cocoa`

wxPython Accessibility

python

# Set accessible name (screen reader label)
control.SetLabel("Descriptive Label")

# Set accessible description (supplementary info)
# Use wx.AccessibleDescription or wx.Accessible subclass

# Keyboard navigation
control.SetFocus()           # Move focus programmatically
panel.SetFocusIgnoringChildren()  # Focus the panel itself

python-development

NPX Install

Tags

SKILL.md Content

Python Development Skill

Python Version Quick Reference

pyproject.toml Skeleton

PyInstaller Quick Reference

One-File Mode

One-Folder Mode

Common Hidden Imports

wxPython Quick Reference

Sizer Cheat Sheet

Thread-Safe GUI Updates

Standard IDs

Event Types

Common Pitfalls

Python

wxPython

Cross-Platform Paths

Testing Quick Reference

Logging Setup Template

Desktop Accessibility Quick Reference

Platform API Summary

wxPython Accessibility