install.py 文件源码

def handle_extra_path(self):
        if self.root or self.single_version_externally_managed:
            # explicit backward-compatibility mode, allow extra_path to work
            return orig.install.handle_extra_path(self)

        # Ignore extra_path when installing an egg (or being run by another
        # command without --root or --single-version-externally-managed
        self.path_file = None
        self.extra_dirs = ''