Initialization in Python
Every Ice-based application needs to initialize the Ice run time, and this initialization returns an Ice.Communicator object.
A Communicator is a local Python object that represents an instance of the Ice run time. Most Ice-based applications create and use a single Communicator object, although it is possible and occasionally desirable to have multiple Communicator objects in the same application.
You initialize the Ice run time by calling Ice.initialize, for example:
import sys, Ice communicator = Ice.initialize(sys.argv)
Ice.initialize accepts the argument list that is passed to the program by the operating system. The function scans the argument list for any command-line options that are relevant to the Ice run time; any such options are removed from the argument list so, when Ice.initialize returns, the only options and arguments remaining are those that concern your application. If anything goes wrong during initialization, initialize throws an exception.
Before leaving your program, you must call Communicator.destroy. The destroy method is responsible for finalizing the Ice run time. In particular, in an Ice server, destroy waits for any operation implementations that are still executing to complete. In addition, destroy ensures that any outstanding threads are joined with and reclaims a number of operating system resources, such as file descriptors and memory. Never allow your program to terminate without calling destroy first.
The general shape of our application becomes:
import sys, traceback, Ice
status = 0
communicator = None
try:
# correct but suboptimal, see below
communicator = Ice.initialize(sys.argv)
# ...
except:
traceback.print_exc()
status = 1
if communicator:
# correct but suboptimal, see below
communicator.destroy()
sys.exit(status)
This code is a little bit clunky, as we need to make sure the communicator gets destroyed in all paths, including when an exception is thrown.
Fortunately, Communicator implements the Python context manager protocol: this allows us to call initialize in a with statement, which destroys the communicator automatically, without an explicit call to the destroy method.
The preferred way to initialize the Ice run time in Python is therefore:
import sys, Ice with Ice.initialize(sys.argv) as communicator: # ... # communicator is destroyed automatically at the end of the 'with' statement