我正在尝试实现一个keep-alive，每隔30秒发送一些数据以保持telnet连接打开。
我的代码每秒都会调用reinitScore。此函数有时会调用calculateWinner，它通过stelnet.send(data)通过telnet发送数据。
问题是，当我在任何函数中调用stelnet.send(data)时，它会引发NameError: global name 'stelnet' is not defined。
我的问题是：为什么stelnet.send(data)会在一个地方工作，而不是另一个地方？
以下是我的代码中涉及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)
我尝试在许多地方将stelnet声明为global变量，但它不会改变任何内容 - 我总是得到“未定义”NameError。
答案 0 :(得分：1)
响应您更新的代码...错误消息仍正确，因为虽然您已在模块级别定义了stelnet，但您已将其定义为太晚了。在calculateWinner函数中使用之后，的定义就会出现。
将你的代码剥离到一个荒谬的最小例子，你正在做这样的事情：
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取决于不存在的名称。它是否有效或崩溃将取决于其他代码是否已定义stelnet 1）calculateWinner可以获取它，以及2）执行calculateWinner之前。
<强>建议
依赖于全局可变状态的函数很难遵循，更不用说正确编码了。要判断什么取决于哪些变量，或者修改它们是什么，或者何时修改它们并不容易。另外，提出一个MCVE比应该更麻烦，因为看起来独立的函数可能不是。
尽可能多地将模块级代码填入main函数，并从if __name__ == '__main__':的主体中调用它（而不是其他任何东西）（因为即使那个实际上是在模块级别。）
考虑这样的事情：
def reinit_score(output_socket, shared_scores):
# Ensuring safe concurrent access to the `shared_scores`
# dictionary is left as an exercise for the reader.
winner = ... # Determined from `shared_scores`.
output_socket.send(winner)
for key in shared_scores:
shared_scores[key] = 0
threading.Timer(
interval=1,
function=reinit_score,
args=[output_socket, shared_scores],
).start()
def main():
output_socket = ... # This was `stelnet`.
shared_scores = {...} # A dictionary with 4 keys: L/R/U/D.
reinit_score(output_socket, shared_scores)
while True:
play_game(shared_scores)
# `play_game` mutates the `shared_scores` dictionary...
if __name__ == '__main__':
main()
这些函数仍然通过它们传递的共享字典连接，但只有显式传递该字典的函数才能更改其内容。
答案 1 :(得分：0)
您的代码无效，因为您没有将stelnet传递给您的函数。