easy_install.py 文件源码

def update_pth(self, dist):
        if self.pth_file is None:
            return

        for d in self.pth_file[dist.key]:  # drop old entries
            if self.multi_version or d.location != dist.location:
                log.info("Removing %s from easy-install.pth file", d)
                self.pth_file.remove(d)
                if d.location in self.shadow_path:
                    self.shadow_path.remove(d.location)

        if not self.multi_version:
            if dist.location in self.pth_file.paths:
                log.info(
                    "%s is already the active version in easy-install.pth",
                    dist,
                )
            else:
                log.info("Adding %s to easy-install.pth file", dist)
                self.pth_file.add(dist)  # add new entry
                if dist.location not in self.shadow_path:
                    self.shadow_path.append(dist.location)

        if not self.dry_run:

            self.pth_file.save()

            if dist.key == 'setuptools':
                # Ensure that setuptools itself never becomes unavailable!
                # XXX should this check for latest version?
                filename = os.path.join(self.install_dir, 'setuptools.pth')
                if os.path.islink(filename):
                    os.unlink(filename)
                f = open(filename, 'wt')
                f.write(self.pth_file.make_relative(dist.location) + '\n')
                f.close()