Python at run-time keeps a lot of information around about the state of the code it's executing, and exposes quite a lot of it to programmers. So, at run time, there is an actual object (an instance of a class) called a module object that is created when a module is imported. It is a genuine Python object and you can do anything with it that you can do with a Python object. It has methods and everything.
When a function definition that gets executed (which isn't the same as the function being executed - normally the definition would be executed once for the function when the module is imported) it creates a function object, which is just a special kind of object that is a wrapper around the executable code. This too is a real object, you can set variables to it, pass it as a parameter, call it's methods, etc.
Importing the module doesn't waste anything; the module is always fully imported (into the sys.modules mapping), so whether you use import sys or from sys import argv makes no odds.
The only difference between the two statements is what name is bound; import sys binds the name sys to the module (so sys -> sys.modules['sys']), while from sys import argv binds a different name, argv, pointing straight at the attribute contained inside of the module (so argv -> sys.modules['sys'].argv). The rest of the sys module is still there, whether you use anything else from the module or not.
There is also no performance difference between the two approaches. Yes, sys.argv has to look up two things; it has to look up sys in your global namespace (finds the module), then look up the attribute argv. And yes, by using from sys import argv you can skip the attribute lookup, since you already have a direct reference to the attribute. But the import statement still has to do that work, it looks up the same attribute when importing, and you'll only ever need to use argv once. If you had to use argv thousands of times in a loop, it could perhaps make a difference, but in this specific case it really does not.
Hence, the choice between one or the other should be based solely on coding style.
In a large module, I'd certainly use import sys; code documentation matters, and using sys.argv somewhere in a large module makes it much clearer what you are referring to than just argv ever would.
If the only place you use argv is in a '__main__' block to call a main() function, by all means use from sys import argv if you feel happier about that:
if __name__ == '__main__':
from sys import argv
main(argv)
I'd still use import sys there myself. All things being equal (and they are, exactly, in terms of performance and number of characters used to write it), that is just easier on the eye for me.
If you are importing something else altogether, then perhaps performance comes into play. But only if you use a specific name in a module many times over, in a critical loop for example. But then creating a local name (within a function) is going to be faster still:
import somemodule
def somefunction():
localname = somemodule.somefunctionorother
while test:
# huge, critical loop
foo = localname(bar)
Best Answer
Technically a static method and a module function behave pretty much identically - In both cases they work like standard functions, the difference being the namespace where they are placed. So the decision is more one of maintainability/readability.
Generally I would use a static method if some or all of these criteria are met: