多线程：两个线程交互运行

这里主要是建立了两个线程锁，运行自己线程调用函数时获得自己的锁，并释放另外一个线程调用函数的锁。

以下运行，获得lock_num锁的时候，释放lock_char锁，反之一样。

from threading import Thread, Lock, main_thread
import time
lock_num = Lock() 
lock_char = Lock()

# 线程类
class MyThread(Thread):
    def __init__(self, thread_id, func, args):
        super().__init__()
        self.thread_id = thread_id
        self.func = func
        self.args = args
        self.count = len(args)
    def run(self):   
        while self.count:
            self.func(self.args)
            self.count -= 1

# 函数一，打印出数字
def print_num(nums):
    lock_num.acquire()
    if len(nums) > 0:
        print(nums.pop(0))
    lock_char.release()
    time.sleep(1)

# 线程2，打印出字符
def print_char(chars):
    lock_char.acquire()
    if len(chars) > 0:
        print(chars.pop(0))
    lock_num.release()
    time.sleep(1)

nums = [1,2,3,4]
chars = ['a', 'b', 'c', 'd']

lock_num.acquire()
t1 = MyThread('thread-1', print_num, nums) # 线程一
t2 = MyThread('thread-2', print_char, chars) # 线程二

t1.start() # 启动线程
t2.start()
t1.join() # 等待所有子线程结束
t2.join()

输出形式如下：

a
1
b
2
c
3
d
4

另外一个方式，利用Condition。但是这里有个问题，在主线程退出之后，子线程不能自动退出。还没找到解决方法。

from threading import Lock, Thread, Condition
from queue import Queue
import time

cdt = Condition()

class ThreadNum(Thread):
    def __init__(self, thread_id, args):
        super().__init__()
        self.thread_id = thread_id
        self.args = args
    
    def run(self):
        while True:
            if cdt.acquire():
                if len(self.args) != 0:
                    print(self.args.pop(0))
                    cdt.notify()
                    cdt.wait()
                else:
                    break
                cdt.release()
                time.sleep(0.3)

class ThreadChar(Thread):
    def __init__(self, thread_id, args):
        super().__init__()
        self.thread_id = thread_id
        self.args = args

    def run(self):
        while True:
            if cdt.acquire():
                if len(self.args) != 0:
                    print(self.args.pop(0))
                    cdt.notify()
                    cdt.wait()
                else:
                    break
                cdt.release()
                time.sleep(0.3)

th1 = ThreadNum('th1', [1,2,3,4,5,6,7,8])
th2 = ThreadNum('th2', ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'])

th1.start()
th2.start()