ez_setup.py 文件源码

def main(argv, version=DEFAULT_VERSION):
    """Install or upgrade setuptools and EasyInstall"""
    try:
        import setuptools
    except ImportError:
        egg = None
        try:
            egg = download_setuptools(version, delay=0)
            sys.path.insert(0,egg)
            from setuptools.command.easy_install import main
            return main(list(argv)+[egg])   # we're done here
        finally:
            if egg and os.path.exists(egg):
                os.unlink(egg)
    else:
        if setuptools.__version__ == '0.0.1':
            print >>sys.stderr, (
            "You have an obsolete version of setuptools installed.  Please\n"
            "remove it from your system entirely before rerunning this script."
            )
            sys.exit(2)

    req = "setuptools>="+version
    import pkg_resources
    try:
        pkg_resources.require(req)
    except pkg_resources.VersionConflict:
        try:
            from setuptools.command.easy_install import main
        except ImportError:
            from easy_install import main
        main(list(argv)+[download_setuptools(delay=0)])
        sys.exit(0) # try to force an exit
    else:
        if argv:
            from setuptools.command.easy_install import main
            main(argv)
        else:
            print "Setuptools version",version,"or greater has been installed."
            print '(Run "ez_setup.py -U setuptools" to reinstall or upgrade.)'