I would like to use a variable that I define in my application inside of a module.
The folder structure:
myapp.py
modules/checkargs.py
modules/init.py (an empty file)
Main app (myapp.py):
_PARAMETERS = {
'stuff': 'here'
}
from modules.checkargs import checkargs
if __name__ == "__main__":
checkargs(sys.argv[1:])
checkargs.py:
def checkargs(argv):
global _PARAMETERS;
#more Python insanity here
The error:
NameError: global name '_PARAMETERS' is not defined
In general, you should avoid this style of programming. Modules shouldn't rely on global variables defined in other modules. A better solution would be to pass _PARAMETERS in to checkargs, or move _PARAMETERS to a file that can be shared by multiple modules.
Generally speaking, relying on global variables is a bad idea. Perhaps the best solution is to pass PARAMETERS directly into your checkargs function.
# checkargs.py
def checkargs(argv, parameters):
...
# myapp.py
if __name__ == "__main__":
checkargs(sys.argv[1:], _PARAMETERS)
If you have data that you want to share between modules, you can place that data in a third module that every other module imports:
# modules/shared.py
PARAMETERS = {...}
# myapp.py
from modules.shared import PARAMETERS
# checkargs.py
from modules.shared import PARAMETERS
There are other solutions, though I think the above two solutions are best. For example, your main program can copy the parameters to the checkargs module like this:
# myapp.py
import checkargs
checkargs._PARAMETERS = _PARAMETERS
...
You could also have checkargs directly reference the value in your main module, but that requires a circular import. Circular imports should be avoided.
Why would it be defined? It's from a different module. Inside checkargs.py, you'd need to do:
from myapp import _PARAMETERS
However:
_ then, since that implies private/protected variables.myapp into the checkargs functions instead of importing it there. If you don't, you're creating a circular import, which is logically terrible and doesn't actually work.
