This is a theoretical question that I have been looking for an answer to for sometime, but could never actually find it.
Suppose I have my main file main.py which has import numpy as np and import helper.
If I have a helper file helper.py, could I use np in helper.py, because I already imported it in main.py, and the only time I would ever use helper.py is via main.py, resulting in numpy always being imported?
No. The python documentation states:
The import statement combines two operations; it searches for the named module, then it binds the results of that search to a name in the local scope.
If the import occurs at the top of a module, local scope will be global - i.e. local to the module.
On the plus side, normally imports will only occur once. Python will search the cache for imports before carrying out an import and will create a reference to a previously imported module if it finds it. This saves have to load a second copy - there's no harm (generally) in having the import statement in both modules.
The first place checked during import search is sys.modules. This mapping serves as a cache of all modules that have been previously imported, including the intermediate paths.
Additionally, from the FAQs:
How do I share global variables across modules?
The canonical way to share information across modules within a single program is to create a special module (often called config or cfg). Just import the config module in all modules of your application;
