将参数传递给 Python 线程时出现类型错误

Question

我正在尝试编写一个简单的线程程序。当我不尝试将任何变量传递给目标函数时，它运行良好。

import threading
import time
import datetime

def my_function():
    thread_start_time = str(datetime.datetime.now())
    thread_start_time_remove_microseconds = thread_start_time[:19]

    print("\n\nThread Execution Start Time: ", thread_start_time_remove_microseconds)
    print("I am being printed by mythread. Sleeping for 5 seconds. Main thread will wait till I finish")
    time.sleep(5)

    thread_end_time = str(datetime.datetime.now())
    thread_end_time_remove_microseconds = thread_end_time[:19]

    print("Thread Execution End Time: ", thread_end_time_remove_microseconds)


def main():
    mythread= threading.Thread(target=my_function, name="thread1")
    mythread.start()

    print("\n\n","=" * 31,"I am printed by the main thread","=" * 31,"\n\n")


if __name__ == "__main__":
    main()

结果为：

Thread Execution Start Time: 

 2018-09-09 17:02:46
 =============================== I am printed by the main thread =============================== 


I am being printed by mythread. Sleeping for 5 seconds. Main thread will wait till I finish
Thread Execution End Time:  2018-09-09 17:02:51

Process finished with exit code 0

但是，当我尝试将变量传递给函数时，出现以下错误：导入线程导入时间导入日期时间

def my_function(one_variable):
    print(one_variable)
    thread_start_time = str(datetime.datetime.now())
    thread_start_time_remove_microseconds = thread_start_time[:19]

    print("\n\nThread Execution Start Time: ", thread_start_time_remove_microseconds)
    print("I am being printed by mythread. Sleeping for 5 seconds. Main thread will wait till I finish")
    time.sleep(5)

    thread_end_time = str(datetime.datetime.now())
    thread_end_time_remove_microseconds = thread_end_time[:19]

    print("Thread Execution End Time: ", thread_end_time_remove_microseconds)


def main():
    mythread= threading.Thread(target=my_function, name="thread1", args=("This is one variable from main"))
    mythread.start()

    print("\n\n","=" * 31,"I am printed by the main thread","=" * 31,"\n\n")


if __name__ == "__main__":
    main()

结果为：

=============================== I am printed by the main thread =============================== 


Exception in thread thread1:
Traceback (most recent call last):
  File "C:\Users\dparvez\AppData\Local\Programs\Python\Python36-32\lib\threading.py", line 916, in _bootstrap_inner
    self.run()
  File "C:\Users\dparvez\AppData\Local\Programs\Python\Python36-32\lib\threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
TypeError: my_function() takes 1 positional argument but 30 were given


Process finished with exit code 0

谁能帮我解释为什么会出现这个错误。

Answer 1

你需要一个逗号来使 args 成为一个元组，如下所示：

mythread= threading.Thread(
    target=my_function
    name="thread1",
    args=("This is one variable from main",))

这是因为 threading.Thread() 期望 args 是一些 iterable 并枚举它以使所有 args 传递给您的函数。

表达式 ("string") 等于 "string" - 它是一个可迭代对象，结果为 ("s", "t", "r" , "i", "n", "g")。不是你想要的。要告诉 Python ("string") 是单元素元组而不是括号表达式，请执行 ("string",).

将参数传递给 Python 线程时出现类型错误

TypeError When Passing Arguments to a Python Thread

python

python-multithreading