On 12/08/2011 06:28 AM, Bastien Semene wrote:
Hi list,
I'm trying to pass a variable to an imported module without singletons.
I've seen in the doc, and tested that I can't use global to do it :
=== module.py ===
def testf():
print test
=== main.py ===
global test
test = 1
imported_module = __import__(module, globals(), locals(), [], -1)
importmodule.testf()
=== output ===
NameError: global name 'test' is not defined
Please paste your code and your stacktrace, don't retype them. In the
above, you spelled 'imported_module" two different ways, and forgot the
quotes around "modue", so it couldn't run. There are probably other
problems, but what's the point?
While I was reading many (many) threads about singleton I read people
claiming that singletons can always be avoided (I can't remeber the
most relevant thread on stackoverflow).
I don't want to start a new debate about singletons, I think Internet
has enough debates yet.
But in my case I'd like to access this variable anywhere and at
anytime without having to pass it as a parameter everywhere (this
variable is a configuration manager object).
How can I achieve that without singletons ?
I'm beginner in Python, that's why I'm maybe missing something obvious.
global variables are global only within their own module, but you
probably knew that.
And using the global keyword in main.py isn't accomplishing anything.
Since you're not inside a def or a class, test is already global, as
soon as you give it a value.
You don't pass values to a module, you load the module. And if the
module doesn't have any top-level code, you can "monkey-patch" it to
your heart's content, on lines following.
If mymodule.py doesn't have a global value test, and you wish it did,
you can simply do something like:
import mymodule
mymodule.test = 42
This attribute of mymodule is totally unrelated to one of the same name
in main.py. if you want to refer to it, or to change it again, from
main.py, you'd have to use mymodule.test.
If the module had top-level code that needed to see your new global,
then you'd have a problem, because you can't put it there till after the
import returns.
Now, most of the time when this sort of thing happens, what you really
want is to define another module whose only purpose is to supply these
common values. That module should get imported by both your script and
your module.
--
DaveA
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