Python 全局变量不起作用

Question

目前，我正在开发一些功能来同时 SSH 访问多个远程设备。我遇到了如下问题。

Traceback (most recent call last):
  File "/Volume/Projects/SSH_Conn.py", line 51, in <module>
    SSH_Thread()
  File "/Volume/Projects/SSH_Conn.py", line 43, in SSH_Thread
    for ip in list_ip:
NameError: global name 'list_ip' is not defined

我很确定我已经在下面的代码中创建了全局参数：

def ip_file():
    **global list_ip**
    ip_list_file = open('ip.txt', 'r')
    ip_list_file.seek(0)
    list_ip = ip_list_file.readlines()
    ip_list_file.close()

def ssh_conn(ip):
    date_time = datetime.datetime.now().strftime("%Y-%m-%d")
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    ssh.connect(ip, port=22, username='x', password='y', look_for_keys=False, timeout=None)
    connection = ssh.invoke_shell()
    connection.send("\n")
    connection.send("ls -l\n")
    time.sleep(2)
    file_output = connection.recv(9999)
    hostname = (re.search(r'(.+)$', file_output)).group().strip('$')
    outFile = open(hostname + "-" + str(date_time) + ".txt", "w")
    outFile.write(file_output)

def SSH_Thread():
    threads_instance = []
    for ip in list_ip:
        ti = threading.Thread(target=ssh_conn, args=(ip,))
        ti.start()
        threads_instance.append(ti)

    for ti in threads_instance:
        ti.join()

SSH_Thread()

我的代码中是否需要使用任何其他参数？

Answer 1

只是 return 函数中的值，而不是处理全局变量。

def ip_file():
    ip_list_file = open('ip.txt', 'r')
    ip_list_file.seek(0)
    list_ip = ip_list_file.readlines()
    ip_list_file.close()
    return list_ip  # return the value, so others can use it.

然后，当你想使用它时，只需调用函数并保存结果：

def SSH_Thread():
    threads_instance = []
    list_ip = ip_file()  # here is where you get the result back
    for ip in list_ip:
        ti = threading.Thread(target=ssh_conn, args=(ip,))
        ti.start()
        threads_instance.append(ti)

    for ti in threads_instance:
        ti.join()

Answer 2

您已经在 ip_file 函数中创建了全局参数 list_ip，但是从未调用函数。

所以快速修复是：

def SSH_Thread():
    threads_instance = []
    ip_file() # <--------------- generate the list
    for ip in list_ip:
        ti = threading.Thread(target=ssh_conn, args=(ip,))
        ti.start()
        threads_instance.append(ti)

    for ti in threads_instance:
        ti.join()

顺便说一下，最好 return 列表而不是将结果存储在全局变量中。

Python 全局变量不起作用

Python Global Variable does not work

paramiko

python-2.7