Menu
I want to use a global variable, Init it once. having a thread safe access.
Can someone share an example please?
552
If you want to simply access a global variable you just use its name. However to change its value you need to use the global keyword. E.g. This would change the value of the global variable to 55.
Threads share all global variables; the memory space where global variables are stored is shared by all threads (though, as we will see, you have to be very careful about accessing a global variable from multiple threads).
Global variables are still not thread safe because there's still no protection against most race conditions. You can still have a scenario where one worker gets a value, yields, another modifies it, yields, then the first worker also modifies it.
The canonical way to share information across modules within a single program is to create a special module (often called config or cfg). Import the config module in all modules of your application; the module then becomes available as a global name.
If you need read-only access and the value is initialized before threads are spawn, you don't need to worry about thread safety.
If that is not the case Python threading library is probably what you need, more precisely locks. A really good read on the subject - http://effbot.org/zone/thread-synchronization.htm with quite a lot of examples.
104
You do have a problem if you are using multiprocessing.Processes. In which case you should take a look at Managers and Queues in the multiprocessing module.
22
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
