locking

问题 I am using Python 3.7 on Windows. What I am trying to do: - lock a method of an instance of a class, when another process has acquired that same lock. Attempts: I have already successfully done this, but I don't want a global variable here for the lock, but instead one completely internal to the class from multiprocessing import Lock, freeze_support,Pool from time import sleep def do_work(name): print(name+' waiting for lock to work...',end='') sleep(2) with lock: print('done!') print(name+'

问题 I am using Python 3.7 on Windows. What I am trying to do: - lock a method of an instance of a class, when another process has acquired that same lock. Attempts: I have already successfully done this, but I don't want a global variable here for the lock, but instead one completely internal to the class from multiprocessing import Lock, freeze_support,Pool from time import sleep def do_work(name): print(name+' waiting for lock to work...',end='') sleep(2) with lock: print('done!') print(name+'

问题 I am using Python 3.7 on Windows. What I am trying to do: - lock a method of an instance of a class, when another process has acquired that same lock. Attempts: I have already successfully done this, but I don't want a global variable here for the lock, but instead one completely internal to the class from multiprocessing import Lock, freeze_support,Pool from time import sleep def do_work(name): print(name+' waiting for lock to work...',end='') sleep(2) with lock: print('done!') print(name+'

问题 I have several workers, each holding its own connection to PostgreSQL. The workers manipulate with different tables. The workers handle parallel requests from outside the system. One of the tables being accessed is the table of users. When some information comes, I first need to ensure there is a record for the user in the table. If there is no record, I wish to create one at first. I'm using the following idiom: if [user does not exist] then [create user] The code of [user does not exist] is

问题 I have several workers, each holding its own connection to PostgreSQL. The workers manipulate with different tables. The workers handle parallel requests from outside the system. One of the tables being accessed is the table of users. When some information comes, I first need to ensure there is a record for the user in the table. If there is no record, I wish to create one at first. I'm using the following idiom: if [user does not exist] then [create user] The code of [user does not exist] is

问题 What is the difference between shared_lock and shared_mutex.lock_shared() other than that the destructor of shared_lock unlocks the associated mutex? Is a shared_mutex the only mutex class I can use with shared_lock ? Why would someone want to use lock_guard instead of unique_lock ? If I have many threads constantly locking for reading ( shared_lock ) a variable and I have a variable that tries to lock it for writing ( unique_lock ), will this writing thread have a priority over the other

问题 What is the difference between shared_lock and shared_mutex.lock_shared() other than that the destructor of shared_lock unlocks the associated mutex? Is a shared_mutex the only mutex class I can use with shared_lock ? Why would someone want to use lock_guard instead of unique_lock ? If I have many threads constantly locking for reading ( shared_lock ) a variable and I have a variable that tries to lock it for writing ( unique_lock ), will this writing thread have a priority over the other

问题 What is the difference between shared_lock and shared_mutex.lock_shared() other than that the destructor of shared_lock unlocks the associated mutex? Is a shared_mutex the only mutex class I can use with shared_lock ? Why would someone want to use lock_guard instead of unique_lock ? If I have many threads constantly locking for reading ( shared_lock ) a variable and I have a variable that tries to lock it for writing ( unique_lock ), will this writing thread have a priority over the other

问题 What is the difference between shared_lock and shared_mutex.lock_shared() other than that the destructor of shared_lock unlocks the associated mutex? Is a shared_mutex the only mutex class I can use with shared_lock ? Why would someone want to use lock_guard instead of unique_lock ? If I have many threads constantly locking for reading ( shared_lock ) a variable and I have a variable that tries to lock it for writing ( unique_lock ), will this writing thread have a priority over the other

问题 I am using a Python 3 sequence like this: lock = threading.Lock() res = lock.acquire(timeout=10) if res: # do something .... lock.release() else: # do something else ... I would prefer to use a with-statement instead of explicit "acquire" and "release", but I don't know how to get the timeout effect. 回答1: You can do this pretty easily with a context manager: import threading from contextlib import contextmanager @contextmanager def acquire_timeout(lock, timeout): result = lock.acquire(timeout