1. 锁（Lock）
锁是最基本的同步原语，用于确保某段代码在同一时间只能被一个线程执行。锁有两种状态：锁定和未锁定。
示例代码
python复制
import threading
lock = threading.Lock()
def critical_section():
with lock:
# 这段代码在同一时间只能被一个线程执行
print(f"Thread {threading.current_thread().name} is in the critical section")
threads = []
for i in range(5):
t = threading.Thread(target=critical_section)
threads.append(t)
t.start()
for t in threads:
t.join()
2. 可重入锁（RLock）
可重入锁（RLock）允许同一个线程多次获取锁，而不会导致死锁。这在递归调用中非常有用。
示例代码
python复制
import threading
rlock = threading.RLock()
def recursive_function(n):
with rlock:
if n > 0:
print(f"Thread {threading.current_thread().name} is in the recursive function with n={n}")
recursive_function(n - 1)
threads = []
for i in range(5):
t = threading.Thread(target=recursive_function, args=(3,))
threads.append(t)
t.start()
for t in threads:
t.join()
3. 信号量（Semaphore）
信号量用于控制对共享资源的访问，允许多个线程同时访问。信号量有一个计数器，表示当前可用的资源数量。
示例代码
python复制
import threading
semaphore = threading.Semaphore(3) # 允许最多3个线程同时访问
def access_resource():
with semaphore:
print(f"Thread {threading.current_thread().name} is accessing the resource")
threading.Event().wait(1) # 模拟资源访问
threads = []
for i in range(10):
t = threading.Thread(target=access_resource)
threads.append(t)
t.start()
for t in threads:
t.join()
4. 事件（Event）
事件用于线程之间的通信。一个线程可以等待事件的发生，而另一个线程可以设置事件。
示例代码
python复制
import threading
event = threading.Event()
def wait_for_event():
print(f"Thread {threading.current_thread().name} is waiting for the event")
event.wait()
print(f"Thread {threading.current_thread().name} received the event")
def set_event():
threading.Event().wait(2) # 模拟一些工作
print(f"Thread {threading.current_thread().name} is setting the event")
event.set()
threads = []
for i in range(3):
t = threading.Thread(target=wait_for_event)
threads.append(t)
t.start()
setter_thread = threading.Thread(target=set_event)
setter_thread.start()
for t in threads:
t.join()
setter_thread.join()
5. 条件变量（Condition）
条件变量用于复杂的线程间同步，允许线程等待某个条件的发生，并在条件满足时被唤醒。
示例代码
python复制
import threading
condition = threading.Condition()
shared_resource = []
def producer():
with condition:
for i in range(5):
shared_resource.append(i)
print(f"Producer added {i}")
condition.notify() # 通知消费者
threading.Event().wait(1) # 模拟生产时间
def consumer():
with condition:
while True:
condition.wait() # 等待生产者的通知
if shared_resource:
item = shared_resource.pop(0)
print(f"Consumer consumed {item}")
else:
break
producer_thread = threading.Thread(target=producer)
consumer_thread = threading.Thread(target=consumer)
producer_thread.start()
consumer_thread.start()
producer_thread.join()
consumer_thread.join()
