python中的全局变量未编辑

Question

我编写了以下代码（简化）将对象添加到一个最初为空的列表（listofeelements，这是一个全局变量）。然而，当我最后打印这个列表时，它仍然是空的。我做错了什么？你知道吗

import threading
def addElement(listOfElements):
   for k in range(10):
      listOfElements.append(k)



listOfElements = []

import threading
def addElement(listOfElements,otherList):
   for k in range(10):
      listOfElements.append(k)



listOfElements = []
threadsElts = []
for i in range(10):
    threadsElts.append(threading.Thread(target=addElement,args=(listOfElements,otherList)))
for t in threadsElts:
    t.start()
for t in threadsElts:
    t.join()

threadsElts = []
for i in range(10):
    threadsElts.append(threading.Thread(target=addElement,args=(listOfElements,otherList)))
for t in threadsElts:
    t.start()
for t in threadsElts:
    t.join()

Answer 1

问题出在代码上。用你的代码，我明白了错误：-你知道吗

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-3:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-4:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-5:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-6:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-7:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-8:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-9:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

Exception in thread Thread-10:
Traceback (most recent call last):
  File "/usr/local/akamai/lib/python2.7/threading.py", line 551, in __bootstrap_inner
  File "/usr/local/akamai/lib/python2.7/threading.py", line 504, in run
TypeError: addElement() takes exactly 1 argument (0 given)

如果像这样传递listOfElements，就可以解决这个问题本文件：你知道吗

threadsElts.append(threading.Thread(target=addElement,args=(listOfElements,)))

进行上述更改后，代码运行良好。你知道吗

另外，请记住，您在修改变量时没有使用任何锁，因此您的代码可能会损坏数据。您可能需要通过以下链接：http://effbot.org/zone/thread-synchronization.htm来更好地理解这个问题

Answer 2

你的问题很简单，TypeError: addElement() takes exactly 1 argument (0 given)。你知道吗

它告诉我们您的问题是函数的param，而您的param是在线程args=(listOfElements)中给出的，看起来不错，但是语法错误。你知道吗

在python中，元组是特殊的，如下所示：

a = () # a has no element
a = (1) # error
a = (1,) # yes, a has one element, the dot cannot be missing, special
a = (1,2) # yes, a has two

你可以试试。你知道吗