How is that state different depending on whether a module has been simply imported (#2. some other block of code has __name__ == "__main__") and the script itself being run (#1. and having __name__=="__main__")?
Ultimately, what I want is for a module to remember (persist) the value of A, regardless of how the module has been loaded into the interpreter. Thanks > Modules retain state their state across all imports in the same > interpreter instance. Module state is not shared among different > instances of the interpreter. > > > For example, consider the two simple modules below. The first method > > fails and I'm not sure exactly why. (Note: assume one instance of an > > interpreter. In my case a 3rd party software tool that starts an > > interpreter when it launches). > > > > Two alternate ways of running it: > > > > 1. (FAILS: RESULTS A = 0) Use the module "test" itself as the driver > > using the conditional statement if (__name__=="__main__"): > > > > test.py > > run2.py > > Ok, what do you mean by this? Do you mean run test.py and then run > run2.py? In so, then you will have *two* instances -- one for each > file being executed. You can only have one main module per > interpreter instance. I suspect this is the source of your confusion. > > > or, > > > > 2. (SUCCES: RESULTS A = 10) Use "run.py" as the driver. > > > > run.py > > > > _________test.py__________________ > > > > import sys,os > > > > A = 0 > > > > def getA(): > > global A > > return A > > > > def run(): > > global A > > A = 10 > > > > if (__name__=="__main__"): > > run() > > Here, A is only initialized when the module is loaded iff it is the > main module. If it's not the main module, then it will have A set to > 0 until some other code calls run(). > > > _________run.py__________________ > > > > import test > > > > test.run() > > print "A = " + str(test.getA()) > > This code calls test.run(), which is necessary for A to be 10. > > > _________run2.py__________________ > > > > import test > > > > print "A = " + str(test.getA()) > > > > -- > > This code gets the value of test.A without calling test.run(). Since > test.run() was not called, A is the value it was initialized when the > test module was loaded -- namely, 0. > > Hope this helps, > > --Nathan Davis -- Peter Bismuti Boeing Information Technology Renton, WA (425) 234-0873 W (425) 442-7775 C -- http://mail.python.org/mailman/listinfo/python-list
