PySide.QtCore.QMutex class provides access serialization between threads.
The purpose of a PySide.QtCore.QMutex is to protect an object, data structure or section of code so that only one thread can access it at a time (this is similar to the Java synchronized 关键词)。通常使用互斥最好采用 PySide.QtCore.QMutexLocker 因为这样使之能轻松确保锁定和解锁被一致履行。
例如，假定有方法每 2 行向用户打印消息：
number = 6
def method1():
number *= 5
number /= 4
def method2():
number *= 3
number /= 2
若连续调用这 2 方法，会发生以下：
# method1()
number *= 5 # number is now 30
number /= 4 # number is now 7
# method2()
number *= 3 # number is now 21
number /= 2 # number is now 10
若从 2 线程同时调用这 2 方法，就会产生以下序列：
# Thread 1 calls method1()
number *= 5 # number is now 30
# Thread 2 calls method2().
#
# Most likely Thread 1 has been put to sleep by the operating
# system to allow Thread 2 to run.
number *= 3 # number is now 90
number /= 2 # number is now 45
# Thread 1 finishes executing.
number /= 4 # number is now 11, instead of 10
若添加互斥，应该获得希望结果：
mutex = QMutex()
number = 6
def method1():
mutex.lock()
number *= 5
number /= 4
mutex.unlock()
def method2():
mutex.lock()
number *= 3
number /= 2
mutex.unlock()
那么仅一线程可以修改 number 在任何给定时间且结果是正确的。当然，这是平凡范例，但适用于事情需要按特定序列发生的任何其它情况。
当调用 PySide.QtCore.QMutex.lock() in a thread, other threads that try to call PySide.QtCore.QMutex.lock() in the same place will block until the thread that got the lock calls PySide.QtCore.QMutex.unlock() . A non-blocking alternative to PySide.QtCore.QMutex.lock() is PySide.QtCore.QMutex.tryLock() .
| 参数： | mode – PySide.QtCore.QMutex.RecursionMode |
|---|
Constructs a new mutex. The mutex is created in an unlocked state.
若 mode is QMutex.Recursive , a thread can lock the same mutex multiple times and the mutex won't be unlocked until a corresponding number of PySide.QtCore.QMutex.unlock() calls have been made. The default is QMutex.NonRecursive .
| 常量 | 描述 |
|---|---|
| QMutex.Recursive | In this mode, a thread can lock the same mutex multiple times and the mutex won't be unlocked until a corresponding number of PySide.QtCore.QMutex.unlock() calls have been made. |
| QMutex.NonRecursive | In this mode, a thread may only lock a mutex once. |
另请参阅
PySide.QtCore.QMutex.QMutex()
Locks the mutex. If another thread has locked the mutex then this call will block until that thread has unlocked it.
Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a recursive mutex . If this mutex is a non-recursive mutex , this function will dead-lock when the mutex is locked recursively.
inline version of QMutex.lock()
| 参数： | timeout – PySide.QtCore.int |
|---|---|
| 返回类型： | PySide.QtCore.bool |
这是重载函数。
Attempts to lock the mutex. This function returns true if the lock was obtained; otherwise it returns false. If another thread has locked the mutex, this function will wait for at most timeout milliseconds for the mutex to become available.
Note: Passing a negative number as the timeout is equivalent to calling PySide.QtCore.QMutex.lock() , i.e. this function will wait forever until mutex can be locked if timeout is negative.
If the lock was obtained, the mutex must be unlocked with PySide.QtCore.QMutex.unlock() before another thread can successfully lock it.
Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a recursive mutex . If this mutex is a non-recursive mutex , this function will always return false when attempting to lock the mutex recursively.
| 返回类型： | PySide.QtCore.bool |
|---|
Attempts to lock the mutex. If the lock was obtained, this function returns true. If another thread has locked the mutex, this function returns false immediately.
If the lock was obtained, the mutex must be unlocked with PySide.QtCore.QMutex.unlock() before another thread can successfully lock it.
Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a recursive mutex . If this mutex is a non-recursive mutex , this function will always return false when attempting to lock the mutex recursively.
| 返回类型： | PySide.QtCore.bool |
|---|
inline version of QMutex.tryLock()
Unlocks the mutex. Attempting to unlock a mutex in a different thread to the one that locked it results in an error. Unlocking a mutex that is not locked results in undefined behavior.
inline version of QMutex.unlock()