os.path.exists() for files in your Path?

I commonly use os.path.exists() to check if a file is there before doing anything with it.

I've run across a situation where I'm calling a executable that's in the configured env path, so it can be called without specifying the abspath.

Is there something that can be done to check if the file exists before calling it? (I may fall back on try/except, but first I'm looking for a replacement for os.path.exists())

btw - I'm doing this on windows.