NameError表示变量未定义，但仅在某些地方定义

Question

我尝试实现一个保持活动，每30秒发送一些数据，以保持telnet连接打开。在

我的代码每秒调用reinitScore。此函数有时会调用calculateWinner，后者通过stelnet.send(data)通过telnet发送数据。在

问题是，当我在任何函数中调用stelnet.send(data)时，它会引发一个NameError: global name 'stelnet' is not defined。在

我的问题是：为什么stelnet.send(data)会在一个地方工作，而不是在另一个地方？在

下面是我的代码中有关telnet传输和函数调用的部分：

import socket, select, string, sys
import string
import threading

leftKeyCounter = 0
rightKeyCounter = 0
frontKeyCounter = 0
backKeyCounter = 0

# function called by reinitScore
def calculateWinner(d):
    scores = {}
    high_score = 0
    for key, value in d.items():
        try:
            scores[value].append(key)
        except KeyError:
            scores[value] = [key]
        if value > high_score:
            high_score = value
    results = scores[high_score]
    if len(results) == 1:
        print results[0]
        stelnet.send(results[0])
        return results[0]
    else:
        print 'TIE'
        return 'TIE', results

#called once and repeat itselfs every second
def reinitScore():
    threading.Timer(1, reinitScore).start()
    #globaling for changing the content
    global leftKeyCounter
    global rightKeyCounter
    global frontKeyCounter
    global backKeyCounter
    values = {'left' : leftKeyCounter, 'right' : rightKeyCounter, 'front' : frontKeyCounter, 'back' : backKeyCounter}
    if (leftKeyCounter != 0 or rightKeyCounter != 0 or frontKeyCounter != 0 or backKeyCounter != 0):
        calculateWinner(values)
        leftKeyCounter = 0
        rightKeyCounter = 0
        frontKeyCounter = 0
        backKeyCounter = 0
        print "back to 0"

reinitScore()
if __name__ == "__main__":

    if(len(sys.argv) < 3) :


    print 'Usage : python telnet.py hostname port'
    sys.exit()

    host = sys.argv[1]
    port = int(sys.argv[2]) 
    stelnet = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    stelnet.settimeout(2)

    # connect to remote host
    try :
        stelnet.connect((host, port))
    except :
        print 'Unable to connect'
        sys.exit()

    print 'Connected to remote host'

    while True:
       // ... Some code that has nothing to do with telnet 

    while 1:
       socket_list = [sys.stdin, stelnet]

        read_sockets, write_sockets, error_sockets = select.select(socket_list , [], [])

        for sock in read_sockets:
            if sock == stelnet:
                data = sock.recv(4096)
                if not data :
                    print 'Connection closed'
                    sys.exit()
                else :
                    sys.stdout.write(data)

            else :
                msg = sys.stdin.readline()
                stelnet.send(msg)

我试图在很多地方将stelnet声明为global变量，但它不会改变任何东西——我总是得到“未定义”NameError。在

Answer 1

为了回应你更新的代码。。。错误消息仍然正确，因为尽管您已经在模块级别定义了stelnet，但是定义它太晚了。它的定义发生在calculateWinner函数中的之后。在

将代码分解为一个可笑的最小示例，您正在执行以下操作：

def calculateWinner():
    # A leap of faith...  There is no `stelnet` defined
    # in this function.
    stelnet.send(results[0])

def reinitScore():
    # Indirectly depends on `stelnet` too.
    calculateWinner()

# But we haven't defined `stelnet` yet...
reinitScore() # Kaboom!

# These lines will never run, because the NameError has
# already happened.
if __name__ == '__main__':
    stelnet = ...  # Too late.

calculateWinner依赖于函数编译时不存在的名称。它是正常工作还是崩溃取决于是否有其他代码定义了stelnet1），其中calculateWinner可以在其中得到，2）在calculateWinner执行之前。在

建议

依赖于全局可变状态的函数很难理解，更不用说正确的代码了。很难判断什么依赖于哪些变量，或者是什么在修改它们，或者什么时候。另外，提出一个MCVE比它应该更麻烦，因为看起来独立的函数可能不是。在

将尽可能多的模块级代码填充到一个main函数中，并从if __name__ == '__main__':的主体调用它（而不是其他任何东西）（因为即使是，那个实际上也在模块级）。在

考虑如下：

^{pr2}$

这些函数仍然由它们传递的共享字典连接，但是只有显式传递给字典的函数才能更改其内容。在