On Sat, Feb 12, 2011 at 7:25 PM, Peter Otten <__pete...@web.de> wrote: > Jean-Daniel wrote: > >> Hello, >> >> I am writing a small framework where the user which writes a function >> can expect some global variable to be set in the function namespace. >> >> The user has to write a function like this: >> """ >> # function.py >> from framework import, command, run >> >> @command >> def myfunc(): >> print HOST >> >> if __name__=="__main__": >> run() >> """ >> >> command() registers the function, and run() evaluates or execute the >> function within an environment or a namespace where HOST has been >> automagically set. >> >> Question: how can write run in a way that when using run() in a >> script, the decorated function will be run with the special names made >> available? >> >> Here is the code for this, which does not work as intended because the >> 'HOST' can not be found when evaluating the decorated function >> >> """ >> # framework.py >> HOST = '192.168.0.1' >> PORT = 12345 >> >> commands = [] >> >> def command(f): >> commands.append(f) >> return f >> >> def run(): >> for f in commands: >> assert globals()['HOST'] >> exec 'f()' in globals(),locals() >> >> if __name__=='__main__': >> >> @command >> def info(): >> print HOST,PORT >> >> run() >> """ >> >> Note that the assert makes sure the HOST variable is indeed present in >> the globals when running the function. When running function.py, I get >> an NameError exception. When I put the func function in the framework >> module and execute framework.py as a script, this works fine, the >> global HOST is available in the func namespace which gets printed. I >> tried many combinations of eval() or exec as well as many combinations >> for the globals() and locals() mapping fed to eval/exec without >> success. > > Every module has its own global namespace, and a function is looking for > global variables in the namespace it is defined in, not the one where the > function is called from. A function defined in Python carries its global > namespace with it as the __globals__ attribute (func_globals in older Python > versions). > > def run(): > for f in commands: > f.__globals__.update(HOST=HOST, PORT=PORT) > f() > > Note that every function in the function's module will see the extra > variables.
Cool, thanks. I read here: http://docs.python.org/reference/datamodel.html about the func_globals and how it is a read only attribute. I incorrectly thought that this dictionary was read only because the reference was read only. > > Peter > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
