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