如何获得system标准输出？ --再问： 如何将stderr 重定向到stdout？

CODE:

ping = os.popen('ping [url]www.google.com[/url]')
for p in ping:
        print p

# output:
################################################
Pinging [url]www.l.google.com[/url] [72.14.205.104] with 32 bytes of data:

Reply from 72.14.205.104: bytes=32 time=23ms TTL=245
Reply from 72.14.205.104: bytes=32 time=23ms TTL=245
Reply from 72.14.205.104: bytes=32 time=22ms TTL=245
Reply from 72.14.205.104: bytes=32 time=21ms TTL=245

Ping statistics for 72.14.205.104:

    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

    Minimum = 21ms, Maximum = 23ms, Average = 22ms