python 包之 threading 多執行緒

import threading

def func(s):
print(s)

if __name__ == '__main__':
# 建立執行緒
thread = threading.Thread(target=func, args=('hello',))
# 啟動執行緒
thread.start()
# 等待執行緒結束
thread.join()

import threading

def func(s):
print(s)

if __name__ == '__main__':
thread = [
threading.Thread(target=func, args=('1', ))
threading.Thread(target=func, args=('2', ))
]

[t.start() for t in thread]
[t.join() for t in thread]

import time
import threading

# 建立鎖
lock = threading.Lock()
# 全域性變數
global_resource = [None] * 5

def change_resource(para, sleep):
# 請求鎖
lock.acquire()
# 這段程式碼如果不加鎖，第一個執行緒執行結束後global_resource中是亂的，輸出為：結果是： ['hello', 'hi', 'hi', 'hello', 'hello']
# 第二個執行緒執行結束後，global_resource中還是亂的，輸出為：結果是： ['hello', 'hi', 'hi', 'hi', 'hi']
global global_resource
for i in range(len(global_resource)):
global_resource[i] = para
time.sleep(sleep)
print("結果是：", global_resource)

# 釋放鎖
lock.release()

if __name__ == '__main__':
thread = [
threading.Thread(target=change_resource, args=('hi', 2))
threading.Thread(target=change_resource, args=('hello', 1))
]

[t.start() for t in thread]
[t.join() for t in thread]

# 結果是： ['hi', 'hi', 'hi', 'hi', 'hi']
# 結果是： ['hello', 'hello', 'hello', 'hello', 'hello']

import time
import threading

# 使用成一個遞迴鎖就可以解決當前這種死鎖情況
rlock_hi = rlock_hello = threading.RLock()

def test_thread_hi():
# 初始時鎖內部的遞迴等級為1
rlock_hi.acquire()
print('執行緒test_thread_hi獲得了鎖rlock_hi')
time.sleep(2)
# 如果再次獲取同樣一把鎖，則不會阻塞，只是內部的遞迴等級加1
rlock_hello.acquire()
print('執行緒test_thread_hi獲得了鎖rlock_hello')
# 釋放一次鎖，內部遞迴等級減1
rlock_hello.release()
# 這裡再次減，當遞迴等級為0時，其他執行緒才可獲取到此鎖
rlock_hi.release()

def test_thread_hello():
rlock_hello.acquire()
print('執行緒test_thread_hello獲得了鎖rlock_hello')
time.sleep(2)
rlock_hi.acquire()
print('執行緒test_thread_hello獲得了鎖rlock_hi')
rlock_hi.release()
rlock_hello.release()

if __name__ == '__main__':
thread = [
threading.Thread(target=test_thread_hi)
threading.Thread(target=test_thread_hello)
]

[t.start() for t in thread]
[t.join() for t in thread]

import time
import threading

# 建立號誌物件，初始化計數器值為3
semaphore3 = threading.Semaphore(3)


def thread_semaphore(index):
# 號誌計數器減1
semaphore3.acquire()
time.sleep(2)
print('thread_%s is running...' % index)
# 號誌計數器加1
semaphore3.release()


if __name__ == '__main__':
# 雖然會有9個執行緒執行，但是通過號誌控制同時只能有3個執行緒執行
# 第4個執行緒啟動時，呼叫acquire發現計數器為0了，所以就會阻塞等待計數器大於0的時候
for index in range(9):
threading.Thread(target=thread_semaphore, args=(index, )).start()