Just like pypiwin32 or comtypes is used to script via COM on windows, appscript is used to script on Mac. Photoshop scripting is exposed via it's scriptable dictionary.

appscript is a high-level, user-friendly Apple event bridge that allows you to control Apple's Scriptable macOS applications from Python.

pip install appscript

Usage:

from appscript import app

psApp = app(id="com.adobe.Photoshop", terms="sdef")
psApp.open("/absolute/reference/to/file.psd")

from appscript import app, k

ps = app(id="com.adobe.Photoshop", terms="sdef")
doc = ps.make(new=k.document, with_properties={k.width: 320, k.height: 240})
layer_ref = doc.make(new=k.art_layer, with_properties={k.kind: k.text_layer})

text_item = layer_ref.text_object
text_item.contents.set("HELLO WORLD")
text_item.position.set([120, 120])

Anything possible in Windows' COM based scripting is also possible in appscript, but I hope the example above shows that the syntax is quite different, and scripts designed for COM do not pass over to the macOS based scripting without tweaking.

Here are a few differences to look out for:

1. The syntax Adobe produces for AppleScript (which appscript bases it's terminology on) is just different to what it produces for the COM API.
2. In appscript, referencing an object or property does not return the value of that object or property, to do that you must call the reference, or its get() method. For example, ps.documents[1].art_layers[1].name returns a reference, not a string of the name. To retrieve the actual value of the layer's name, you must call it ps.documents[1].art_layers[1].name(). To set the value, you call ...art_layers[1].name.set(value)
3. When using comtypes, you need to manually define constants/enums (e.g. the values for RulerUnits that are used a lot in the examples here). This is not the case with appscript, they are parsed from the terminology and stored in a global k object.
4. Keyword arguments! As mentioned in the appscript documentation, if an argument (a.k.a. a parameter) has a keyword in the AppleScript documentation, it must have that keyword when you call it.
5. AppleScript container indcies start at 1, not 0, and appscript inherits this. If you're iterating over a list of appscript objects using enumerate(...) or range(len(...)), always start at 1, or add 1.

The most up‑to‐date reference for functions, arguments, keywords, and other Photoshop specific information will always be the Scripting Dictionary that comes with your install of Photoshop.

You can access this by opening the Script Editor app, then going to: File > Open Dictionary... > Adobe Photoshop 20XX.app.

To translate this to appscript syntax, you can simply follow the rules specified here:

• Replace "&" with "and"
• Replace any remaining spaces or symbols with "_"
• Any names that are a reserved Python keyword (i.e. "def", "class", "in", "from") have an "_" appended to the end

The developer of appscript has a tool called ASDictionary which can be useful as a reference.

It's worth having a cursory browse of appscript's documentation to get a feel for how to translate AppleScript documentation for use in appscript. It's very verbose though, be warned.

See Photoshop CC 2018 doc/reference for an appscript specific reference.

Also see Adobe's AppleScript developer reference.