NameError: global name 'interfaceName' is not defined even though it is

Question

def putCardMon():
    interfaceName = input(('Type an interface name to put in monitor mode: '))
    print(colored('[+] ', 'green') + 'Trying to put the interface ' + colored(interfaceName, 'yellow') + ' in monitor mode\n')
    call(["sudo ifconfig " + interfaceName + " down; sudo iwconfig " + interfaceName + " mode monitor; sudo ifconfig " + interfaceName + " up"], shell=True)
    interfaceMonCheck = Popen(["iwconfig " + interfaceName + " | grep Mode | cut -d ':' -f2 | cut -d ' ' -f1"], shell=True, stdout=PIPE, universal_newlines=True).communicate()[0].rstrip()
    sleep (1)

---//lots of code before the putCardMon is called//---

interfacesList = Popen("ifconfig -a | grep Link | cut -d ' ' -f1", shell=True, stdout=PIPE, universal_newlines=True).communicate()[0].rstrip()
print('The available interfaces are:\n' + interfacesList + '\n')
putCardMon()
print('Checking if ' + interfaceName + ' is really in monitor mode.')
if interfaceMonCheck == 'Managed':
    print('The interface ' + colored(interfaceName, "green") + ' is not in monitor mode! Check if you typed the interface name correctly or contact support.\n')
    putCardMon()
elif interfaceMonCheck == 'Monitor':
    print(colored('The interface ' + colored(interfaceName, "green") + ' is in monitor mode!'))
    pass
else:
    print(colored('There was an unexpected error. Contact support!\n', "red"))
    exit()

脚本工作正常，函数完成了它的工作，但是当它到达检查部分时，一切都变得糟糕了。

Traceback (most recent call last):
  File "script.py", line 76, in <module>
    print('Checking if ' + interfaceName + ' is really in monitor mode.')
NameError: name 'interfaceName' is not defined

给字符串赋值的函数已经被调用并成功赋值了，怎么会没有定义interfaceName呢？

我在堆栈溢出中搜索了同样的错误，但所有线程都得到了回答，要么是缩进错误，要么是函数是在调用后定义的，这里都不是这种情况。我真的别无选择。我什么都试过了。

Answer 1

来自https://python-textbok.readthedocs.io/en/1.0/Variables_and_Scope.html#variable-scope-and-lifetime

A variable which is defined inside a function is local to that function. It is accessible from the point at which it is defined until the end of the function

您的变量 interfaceName 仅在函数 putCardMon() 的范围内定义。它在函数范围之外不复存在。因此你得到了错误。

如果你想在函数体之外使用变量，考虑返回它并保存它的值。

def putCardMon():
    interfaceName = input(('Type an interface name to put in monitor mode: '))
    print(colored('[+] ', 'green') + 'Trying to put the interface ' + colored(interfaceName, 'yellow') + ' in monitor mode\n')
    call(["sudo ifconfig " + interfaceName + " down; sudo iwconfig " + interfaceName + " mode monitor; sudo ifconfig " + interfaceName + " up"], shell=True)
    interfaceMonCheck = Popen(["iwconfig " + interfaceName + " | grep Mode | cut -d ':' -f2 | cut -d ' ' -f1"], shell=True, stdout=PIPE, universal_newlines=True).communicate()[0].rstrip()
    sleep (1)
    return interfaceName

# Later you can do this
interfaceName = putCardMon()

NameError: global name 'interfaceName' is not defined even though it is

NameError: global name 'interfaceName' is not defined even though it is

python

popen

nameerror