test_subprocess.py 文件源码

def test_preexec(self):
        # DISCLAIMER: Setting environment variables is *not* a good use
        # of a preexec_fn.  This is merely a test.
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;'
                              'sys.stdout.write(os.getenv("FRUIT"))'],
                             stdout=subprocess.PIPE,
                             preexec_fn=lambda: os.putenv("FRUIT", "apple"))
        self.addCleanup(p.stdout.close)
        self.assertEqual(p.stdout.read(), b"apple")