Theoretically, there can be dialects or languages other than plain ordinary AppleScript. I think these are called something like "OSA Language components". For example, googling osa language
OSA is a plugin mechanism for scripting language interpreters. In theory, an OSA-aware application can load and run scripts written in any scripting language, as long as an interpreter for that language has been packaged as a C-based Component Manager component. CM was basically the classic Mac equivalent to Windows' COM, commonly used for Quicktime codecs plugins and other dynamically loaded code bundles, though it's pretty much been superseded by NSBundles and ObjC classes.
In practice, however, AppleScript is the only OSA language that has ever been good enough for production use. The only third-party OSA language components were either really, really limited
Getting back to Python editors... As others have noted, the OP's screenshot is basically fake: you can write Python code in any text editor (even Script Editor), but you won't get syntax highlighting or be able to run it unless you use an editor that has those features built in. Even if you did have a working Python OSA component, SE's a miserably poor tool. Personally, I use TextWrangler - it's basic but free (I recommend customizing the preferences to bind the Run menu item to Cmd-R). There's plenty other options if that's not to your taste - the Python wiki includes a list of editors
which may be a useful starting point.