on running under windows here. whenever i try to add library directories to build_ext on the commandline i'm getting an error. File "c:\python\lib\distutils\command\build_ext.py", line 159, in finalize_options self.library_dirs.append(os.path.join(sys.exec_prefix, 'libs')) AttributeError: append it turns out that library_dirs is a string type. in build_ext.py line 143 it looks like the code is checking for strings in self.libraries. from my quick look it would solve the problem to also check library_dirs also. also, the commandline help for -L says to pass all library directories in a semicolon separated list. when i do this the self.library_dirs is still just a string containing my list with the semicolons. (it wouldn't seem like this gets split later on?) using multiple include paths with the semicolons does appear to work correctly. although i would probably prefer to allow multiple -I flags. (currently the 'last' -I flag overrides the previous) am i correct in guessing these commandline arguments aren't used too often? i'm thinking i'll just parse -I and -L arguments off of the commandline myself for now. although i'm also seeking better advice :]