在python中每N次运行一个方法

Question

我试图每 5 秒打印一个句子，我需要向它传递一个参数。我在用threadingimport threadingdef printit(whatever):  threading.Timer(5.0, printit).start()  print(whatever)var= "start"printit(var)这给了我这个错误C:\Users\Wei Xi\Desktop>python test.pystartException in thread Thread-1:Traceback (most recent call last):  File "C:\Users\Wei Xi\AppData\Local\Programs\Python\Python38\lib\threading.py", line 932, in _bootstrap_inner    self.run()  File "C:\Users\Wei Xi\AppData\Local\Programs\Python\Python38\lib\threading.py", line 1254, in run    self.function(*self.args, **self.kwargs)TypeError: printit() missing 1 required positional argument: 'whatever'```

Answer 1

threading.Timer构造函数接受各个目标函数 ( ) 的args关键字参数：kwargsclass threading.Timer(interval, function, args=None, kwargs=None)

import threading

def printit(whatever):

  threading.Timer(5.0, printit, args=(whatever,)).start()

  print(whatever)

var= "start"

printit(var)

示例输出将是（在“无限”打印中）：

start

start

start

start

...

Answer 2

这是可能的解决方案之一：

import threading

def printit(whatever): 

    print(whatever)

    threading.Timer(5.0, printit, {whatever}).start() 

var = "start" 

printit(var)

您收到错误是因为您在whatever递归调用printit函数时没有传入（函数参数）。

编辑：

但是，此解决方案将产生无限数量的线程。如果您想将该进程作为后台任务运行，您可以这样做只使用一个线程。

注意：我在这个例子中使用了 2 个参数。

import time

import threading

def printit(whatever, whatever2, seconds=5):

    while True:

        print(whatever)

        print(whatever2)

        time.sleep(seconds)

var = "start"

var2 = "end"

threading.Thread(target=printit, kwargs={"whatever":var, "whatever2":var2, "seconds":5}).start() 

print("Do something else")

输出：

start

end

Do something else

start

end

start

end

... (repeat start end every 5 seconds)

Answer 3

你可以使用时间：

def printit(str_):

   time.sleep(5)

   print(str_)

var = "start"

while True:

     printit(var)

Answer 4

您可以time.sleep()在 while 循环中使用该函数：

import time

def printit(whatever, seconds=5):

    while True:

        print(whatever)

        time.sleep(seconds)

var= "start"

printit(var) # prints "start" every 5 seconds

#start

#start

#start