Python计时器“NoneType"对象不可调用错误 [英] Python timer 'NoneType' object is not callable error

问题描述

我想做一个程序，每 10 秒检查一次给定的 url

I want to make a program which is checks the given url for every 10 seconds

def listener(url):
    print ("Status: Listening")
    response = urllib.request.urlopen(url)
    data = response.read()
    text = data.decode('utf-8')
    if text == 'Hello World. Testing!':
        print("--Action Started!--")


t = Timer(10.0,listener('http://test.com/test.txt'))
t.start()

这里是输出:

Status: Listening
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python3.4/threading.py", line 920, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.4/threading.py", line 1186, in run
    self.function(*self.args, **self.kwargs)
TypeError: 'NoneType' object is not callable

运行一次，10秒后出现错误

It runs the function for one time, after 10 seconds the error appears

推荐答案

目前，您的 listener 函数调用的结果正在提供给 Timer，结果是 None，因为您需要进行显式返回，以便您的 Timer 可以进行操作.

Currently, the result of your listener function call is being given to Timer, which is resultantly None, as you need to make an explicit return so your Timer has something to operate on.

您必须将 listener() 的参数放在另一个参数中，就像这样.请注意，args 必须是一个序列，因此带逗号的元组放在 url 之后.如果没有这个元组，您会将 'http://test.com/test.txt' 中的每个字符作为参数传递给 listener.

You have to place the argument for your listener() in another parameter, like this. Note that args must be a sequence, thus the tuple with the comma placed after your url. Without this tuple, you are passing each individual character from 'http://test.com/test.txt' as an argument to listener.

t = Timer(10.0,listener,args=('http://test.com/test.txt',))

正如您在文档此处中所见，参数必须作为第三个参数传递.

As you can see in documentation here, arguments must be passed as a third parameter.

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