添加子进程时出错：变量未定义

Question

我的脚本会接收一些参数，比如

C:\> python lookup.py "sender-ip=10.10.10.10"

然后它会获取发送者的IP地址，并查找WMI信息。

现在我在获取WMI信息之前，添加了一个ping子进程来先检查机器是否在线，但我遇到了以下错误：

C:\> python lookup.py "sender-ip=10.10.10.10"
Traceback (most recent call last):
  File "lookup.py", line 10, in <module>
    ["ping", "-n", "1", userIP],
NameError: name 'userIP' is not defined

接着我尝试在程序开始时定义一个userIP的全局变量，但又出现了错误：

C:\> python lookup.py "sender-ip=10.10.10.10"
Traceback (most recent call last):
  File "lookup.py", line 10, in <module>
    ["ping", "-n", "1", userIP],
NameError: global name 'userIP' is not defined

这是程序的代码（没有全局声明的部分）：

# import statements
import sys, wmi, subprocess

# subprocess
ping = subprocess.Popen(
    ["ping", "-n", "1", userIP],
    stdout = subprocess.PIPE,
    stderr = subprocess.PIPE
)

# get the arguments and extract user's IP address
argument = sys.argv[1]
attr_map = dict(item.strip().split('=') for item in argument.split(','))
userIP =  attr_map['sender-ip']
print userIP

# can we ping the user's IP address?
out, error = ping.communicate()

# if we cannot ping user's IP address then print error message and exit program
if out.find("Reply from") == -1:
    print userIP, "is NOT pingable."
    sys.exit()

# remaining lines will execute if we can ping user's IP address
c = wmi.WMI(userIP)
for os in c.Win32_OperatingSystem():
  print os.Caption

Answer 1

这里不需要全局变量。只需在使用之前给userIP赋值就可以了：

# import statements
import sys, wmi, subprocess

# get the arguments and extract user's IP address
argument = sys.argv[1]
attr_map = dict(item.strip().split('=') for item in argument.split(','))
userIP =  attr_map['sender-ip']
print userIP

# subprocess
ping = subprocess.Popen(
    ["ping", "-n", "1", userIP],
    stdout = subprocess.PIPE,
    stderr = subprocess.PIPE
)

# can we ping the user's IP address?
out, error = ping.communicate()

# if we cannot ping user's IP address then print error message and exit program
if out.find("Reply from") == -1:
    print userIP, "is NOT pingable."
    sys.exit()

# remaining lines will execute if we can ping user's IP address
c = wmi.WMI(userIP)
for os in c.Win32_OperatingSystem():
  print os.Caption