Python TypeError:'；的操作数类型不受支持；datetime.datetime'；和'；str'；

我正在尝试使用python构建一个网络监视器，它通过向外部资源发送ping请求来持续监视internet连接。它还记录了互联网何时停机以及停机时间。在运行这个python程序时，我发现了一个错误

    import socket
    import time
    import datetime
    import os
    import sys
        
    LOG_FNAME = "network.log"
    FILE = os.path.join(os.getcwd(), LOG_FNAME)
    def send_ping_request(host="1.1.1.1", port=53, timeout=3):
        try:
            socket.setdefaulttimeout(timeout)
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.connect((host,port))
        except OSError as error:
            return False
        else:
            s.close()
            return True
    def write_permission_check():
        try:
            with open(FILE, "a") as file:
                pass
        except OSError as error:
            print("Log file creation failed")
            sys.exit()
        finally:
            pass

    def calculate_time(start, stop):
        time_difference = stop - start
        seconds = float(str(time_difference.total_seconds()))
        return str(datetime.timedelta(seconds=seconds)).split(".")[0]
    def mon_net_connection(ping_freq=2):
        monitor_start_time = datetime.datetime.now()
    def motd():
        motd = "Network connection monitoring started at: " + 
    str(monitor_start_time).split(".")[0] + " Sending ping request in " + str(ping_freq) + " seconds"
        print(motd)

    with open(FILE, "a") as file:
        file.write("\n")
        file.write("motd" + "\n")
    while True:
        if send_ping_request():
            time.sleep(1)
        else:
            down_time = datetime.datetime.now()
            fail_msg = "Network Connection Unavailable at: " +str(down_time).split(".")[0]
            print(fail_msg)
            with open(FILE, "a") as file:
                file.write(fail_msg + "\n")
                i = 0
            while not send_ping_request():
                time.sleep(1)
                i += 1
                if i >= 3600:
                    i = 0
                    now = datetime.datetime.now()
                    continous_message = "Network Unavailabilty Persistent at: " +str(now).split(".")[0]
                    print(continous_message)
                    with open(FILE, "a") as file:
                        file.write(continous_message + "\n")
                up_time = datetime.datetime.now()
                uptime_message = "Network Connectivity Restored at: " +str(up_time).split(".")[0]
 
                down_time = calculate_time(down_time, up_time)
                _m = "Network Connection was Unavailable for " + down_time
 
                print(uptime_message)
                print(_m)
 
                with open(FILE, "a") as file:
                    file.write(uptime_message + "\n")
                    file.write(_m + "\n")
        mon_net_connection()

我得到的错误如下

    Traceback (most recent call last):
      File "C:\Users\samsung\AppData\Local\Programs\Python\Python39\checknetwork1.py", line 
    64, in <module>
        down_time = calculate_time(down_time, up_time)
      File "C:\Users\samsung\AppData\Local\Programs\Python\Python39\checknetwork1.py", line 29, in calculate_time
        time_difference = stop - start
    TypeError: unsupported operand type(s) for -: 'datetime.datetime' and 'str' 

回溯（最近一次呼叫最后一次）：
文件“C:\Users\samsung\AppData\Local\Programs\Python\Python39\checknetwork1.py”，第行
64，在
停机时间=计算停机时间（停机时间、停机时间）
文件“C:\Users\samsung\AppData\Local\Programs\Python\Python39\checknetwork1.py”，第29行，计算时间
时差=停止-启动
TypeError:-：“datetime.datetime”和“str”的操作数类型不受支持

---

请帮助解决此错误。我无法找出错误的位置以及如何更正。

变量

down\u time

最初设置为type

datetime。datetime

与

up\u time

变量一样。问题出在

的
循环中，对
计算时间（）
的第一次调用返回一个
str
，该str被分配到
下一次循环中调用时，该类型将不起作用

我不完全确定循环试图完成什么，但如果您想保持这种模式，您需要
calculate\u time
返回
datetime.datetime
对象，并在需要打印或记录时显式将其强制转换为
str
。
down\u time=calculate\u time（down\u time，up\time）
-
计算时间
返回字符串。您正在将其分配给
停机时间
。然后在随后的循环迭代中，您将返回到
计算时间
…