Does scons know in which directory a SConscript file resides?

We are evaluating scons as a build system, and I am having a problem accomodating our old system. In some of our source code subdirectories, we have a "sources.lib" file that lists the names of the C++ files that need to be compiled to assemble that directory's target library. But, there are additional C++ files in the same directory, so I can't just use Glob() to find the appropriate ones.

How do I find out which directory a SConscript file resides in? os.getcwd() always returns the build directory. Even though the documentation states that paths in a SConscript are relative to the source directory (or else Glob('*.cpp') wouldn't work), just doing an open('sources.lib') fails because it looks for the file in the build directory. Finally, the build environment in that SConscript file doesn't contain the actual current source directory.

Edit From this reply it looks like

File('sources.lib').srcnode().abspath

returns the proper filename and directory, but it won't tell you if it exists (must use os.path.isfile for that). It also appears that

Dir('.').srcnode().abspath

will tell you where the SConstruct file resides.

Example When defining which source files to compile for a library, I don't want to use

lib = env.SharedLibrary('mylib', Glob('*.cpp'))

but instead would rather construct a function that first checks for the existence of "sources.lib" and if it does not exist, use globbing. So I'm defining my library like so

lib = env.SharedLibrary('mylib', env.getSources('*.cpp'))

and making a function that reads the file if it exists

def getSources(self, pattern):

    # list of source files to assign to a target
    sources =