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Windows backends: comtypes vs win32com

Photoshop on Windows is automated through COM. Two popular Python bridges:

comtypes win32com (pywin32)
Package comtypes pywin32
Arrays / nested tuples Generally better (e.g. selection coordinates) Often fails or needs VARIANT wrappers
Early-bound wrappers GetModule / type libs makepy / EnsureDispatch
SolidColor / create CreateObject(...) Dispatch(...)
Community samples Growing Very common in older code

Recommendation

  1. Default to comtypes for new samples and tools (this repo’s get_app() does that in auto mode).
  2. Use win32com when you are pasting Action Manager code generated against win32com examples, or when you rely on makepy wrappers under api_reference/.
  3. Do not import both into the same module unless you know why — it confuses readers and can create two different proxy objects.

Selection example

This pattern historically fails with raw win32com but works with comtypes:

from photoshop_scripting import get_app
from photoshop_scripting.constants import SelectionType

app = get_app(backend="comtypes")
doc = app.ActiveDocument
area = ((0, 0), (100, 0), (100, 100), (0, 100))
doc.Selection.Select(area, int(SelectionType.REPLACE), 0, False)

Connecting

from photoshop_scripting import get_app

app = get_app()                      # auto backend, prefer running instance
app = get_app(backend="comtypes")
app = get_app(backend="win32com")
app = get_app(prefer_running=False)  # force launch

Elevation gotcha

If Photoshop is running as Administrator and your Python process is not (or vice versa), COM attach fails. Run both at the same integrity level.

macOS

macOS does not use COM. Use appscript and the samples under sample_scripts/mac_scripting/. Syntax does not port 1:1 — see that folder’s README.