App class - check for installed app without running it --- will not be implemented

Verifying if app is installed(correctly) will differ between OSes. I think it is not part of App class. I would suggest to implement it outside of sikuli (or if jyhton/java is an option you can use code directly in sikui)

When the app executive is given with an absolute path, the existence is checked and in case an error message is created.

But you may simply try app.open(), it either works or does not.

It might be helpful, what exactly you would expect from such a feature.

Just to be sure i'm searching for the app registry key and version System name.

def isAlreadyInstalled(lookupRegistryKey):
    consoleLines = os.popen('reg query "' + expectedRegistryKey + "\\" + expectedVersionSystemName + '"').readlines()
    if len(consoleLines) == 0:
        return False
    return True

ok, understood.

But this is only valid for applications, that are installed by the appropriate Windows installation services (hence shown in the list of installed programs and can be uninstalled there).

Please confirm.

Exactly, forgot to mention this. If the app is not installed via windows installer it won't work

expectedVersion = "appNameVersion"
expectedRegistryKey = "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths" - this is kinda standard in this case

Thanks for information,but this is a very special Windows-only feature, that I will not implement.