变量不返回。赋值前引用

Question

import os.path
import re
import socket
host = ''
port = 6366
s = socket.socket (socket.AF_INET, socket.SOCK_STREAM)
s.bind ((host, port))
def request ():
    print ("What file should I write to?")
    file = input ()
    thing = os.path.exists (file)
    if thing == True:
        start = 0
    elif file.endswith ('.txt'):
        stuff = open (file, "w")
        stuff.write ("Requests on what to add to the server. \n")
        stuff.close ()
        start = 0
    else:
        start = 1
    go = "yes"
    list1 = (start, file, go)
    return list1
start = 1
while start == 1:
    list1 = request ()
    (start, file, go) = list1
def loop ():
    print ("Listening for requests.")
    s.listen (1)
    conn, addr = s.accept ()
    print ("Connected to {0}".format(addr))
    while 1:
        want = conn.recv(1024).decode()
        if not want:
            break
        if want == "shutdown":
            thingy = "no"
        print ("Writing to {0}".format(file))
        x = open (file, "a")
        x.write (want + "\n")
        x.close ()
        print ("Done writing to {0}".format(file))
    x = open (file, "a")
    x.write (format(addr) + "\n")
    x.close ()
    print ("Disconnecting from {0}".format(addr))
    conn.close()
    print ("Disconnected from {0}".format(addr))
    return thingy
while go == "yes":
    go = loop ()
if go == "no":
    print ("Shutting down")

这是一个服务器。每当我在第 50 行尝试 return "thingy" 时，我都会收到以下错误。

Traceback (most recent call last):
  File "H:\Python\Server Requests\Listen.py", line 52, in <module>
    go = loop ()
  File "H:\Python\Server Requests\Listen.py", line 50, in loop
    return thingy
UnboundLocalError: local variable 'thingy' referenced before assignment

我不明白为什么会出现此错误。我没有在那个循环之外引用它。有什么我想念的吗？

Answer 1

尝试声明一个空变量，然后在满足条件的情况下赋值。您的 return 声明将起作用。

Answer 2

对于那个错误；

def loop ():
    print ("Listening for requests.")
    thingy=""
    s.listen (1)
    conn, addr = s.accept ()
    print ("Connected to {0}".format(addr))

只需在函数中添加一个名为thingy 的空变量。它应该可以解决您的问题。

变量不返回。赋值前引用

Variable not returning. Referenced before assignment

python

variables

while-loop