python3多线程写入文件

Question

嗨，我现在刚接触多线程并试图解决这个问题：

• 有一个包含75个元素的
• 写入8个文件的列表，其中不超过10个元素(例如:从索引0到9，文件2-从索引10到19，.，文件8-从索引70到74)
• 使用5个线程来处理，每个线程处理一个单独的文件写入，一个线程将处理多个文件

在开始时，我只是尝试使用线程打印：

import threading
a = list(range(75))

class myThread(threading.Thread):
    def __init__(self, threadID, name, file_number):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.file_number = file_number

    def run(self):
        print("Starting " + self.name)
        print_time(self.name, self.file_number)
        print("Exiting " + self.name)

def print_time(threadName, file_number):
  render_list = a[:10]
  print("%s: %s" % (threadName, render_list))
  del a[:10]


# Create new threads
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
thread3 = myThread(3, "Thread-3", 3)
thread4 = myThread(4, "Thread-4", 4)
thread5 = myThread(5, "Thread-5", 5)
thread6 = myThread(5, "Thread-5", 6)
thread7 = myThread(5, "Thread-5", 7)
thread8 = myThread(5, "Thread-5", 8)

# Start new Threads
thread1.start()
thread2.start()
thread3.start()
thread4.start()
thread5.start()
thread6.start()
thread7.start()
thread8.start()
thread1.join()
thread2.join()
thread3.join()
thread4.join()
thread5.join()
thread6.join()
thread7.join()
thread8.join()
print("Exiting Main Thread")

印得很完美：

Starting Thread-1
Thread-1: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Exiting Thread-1
Starting Thread-2
Thread-2: [10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
Exiting Thread-2
Starting Thread-3
Thread-3: [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]
Exiting Thread-3
Starting Thread-4
Thread-4: [30, 31, 32, 33, 34, 35, 36, 37, 38, 39]
Exiting Thread-4
Starting Thread-5
Thread-5: [40, 41, 42, 43, 44, 45, 46, 47, 48, 49]
Exiting Thread-5
Starting Thread-5
Thread-5: [50, 51, 52, 53, 54, 55, 56, 57, 58, 59]
Exiting Thread-5
Starting Thread-5
Thread-5: [60, 61, 62, 63, 64, 65, 66, 67, 68, 69]
Exiting Thread-5
Starting Thread-5
Thread-5: [70, 71, 72, 73, 74]
Exiting Thread-5
Exiting Main Thread

但当我试图写文件时：

import threading
a = list(range(75))

class myThread(threading.Thread):
    def __init__(self, threadID, name, file_number):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.file_number = file_number

    def run(self):
        print("Starting " + self.name)
        print_time(self.name, self.file_number)
        print("Exiting " + self.name)

def print_time(threadName, file_number):
  render_list = a[:10]
  f = open("demofile_%s.txt" % file_number, "a")
  for i in render_list:
    f.write("%s\n" % i)
  f.close()
  print("%s: %s" % (threadName, render_list))
  del a[:10]


# Create new threads
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
thread3 = myThread(3, "Thread-3", 3)
thread4 = myThread(4, "Thread-4", 4)
thread5 = myThread(5, "Thread-5", 5)
thread6 = myThread(5, "Thread-5", 6)
thread7 = myThread(5, "Thread-5", 7)
thread8 = myThread(5, "Thread-5", 8)

# Start new Threads
thread1.start()
thread2.start()
thread3.start()
thread4.start()
thread5.start()
thread6.start()
thread7.start()
thread8.start()
thread1.join()
thread2.join()
thread3.join()
thread4.join()
thread5.join()
thread6.join()
thread7.join()
thread8.join()
print("Exiting Main Thread")

我的文件中的内容是错误的，并且有复制，如下所示：

Starting Thread-1
Starting Thread-2
Starting Thread-3
Starting Thread-4
Thread-1: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Exiting Thread-1
Thread-3: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Exiting Thread-3
Thread-4: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Exiting Thread-4
Starting Thread-5
Thread-2: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Starting Thread-5
Thread-5: [30, 31, 32, 33, 34, 35, 36, 37, 38, 39]
Exiting Thread-2
Exiting Thread-5
Thread-5: [30, 31, 32, 33, 34, 35, 36, 37, 38, 39]
Starting Thread-5
Exiting Thread-5
Starting Thread-5
Thread-5: [60, 61, 62, 63, 64, 65, 66, 67, 68, 69]
Thread-5: [60, 61, 62, 63, 64, 65, 66, 67, 68, 69]
Exiting Thread-5
Exiting Thread-5
Exiting Main Thread

似乎线程不是按照打印的顺序运行的。

希望有人能帮我解决这个问题

Answer 1

在你开始之前，你应该知道两件事：

Python中的

1. 实际上并不存在多线程，因为python执行架构不允许多线程，为此我建议您使用Linux C。
2. --执行顺序没有受到保护，调度程序按照它想要的顺序执行，所以您可以使用一些阻塞机制，这样的信号量“实际上”按您想要的顺序执行，这是因为您不知道什么时候要执行某些行，有时您需要控制系统资源。

需要记住的一个关键概念是线程异步，也许在创建时，一个线程可以完成，而另一个线程在运行时不要紧，所以您有IPC()机制，用于对进程和线程进行适当的操作。

假设您向某个网站发出请求，而您的PC一直冻结到请求执行为止，这将是很烦人的，因此线程不能执行同步任务。

所以，这就是为什么你没有按顺序看到输出的原因。

现在让我们来处理重复错误：

因为执行命令不能得到保证，而且没有保护就可以访问全局变量，所以您将得到一些不需要的错误，比如重复的数字。

您需要使用一些阻塞技术来读取共享资源。