Question

我编写了以下代码（简化），将对象添加到最初为空的列表（listOfElements，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？

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

问题在于代码。使用您的代码，我收到此错误： -

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)

如果你像这样传递listOfElements，可以解决这个问题： -

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

进行上述更改后代码运行正常。

另外，请记住，您正在修改变量而不进行任何锁定，因此您的代码可能会损坏您的数据。您可能需要浏览此链接：http://effbot.org/zone/thread-synchronization.htm以便更好地了解问题

Answer 2

您的问题很简单，TypeError: addElement() takes exactly 1 argument (0 given)。

它告诉我们你的问题是函数的参数，而你的参数是在线程args=(listOfElements)中给出的，它看起来不错，但语法错误。

在python中，元组很特殊，看看这个：

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

你可以尝试一下。

不编辑python中的全局变量

2 个答案: