FAQ
I have a main module doStuff.py and another module utility.py. At the
start of doStuff.py I call

import utility.py

Then I also proceed to initiallize some global variables

sName = ""

Then I create a class, some methods etc. In one of the methods I assign
a value to my variable sName. Then I call a function from within
my utility.py file:

utility.makeOne(stuff)


Within my utility.py file, I define the makeOne function. But I want to
use that same global variable "sName" In utility.py I have tried to
indicate that I'm using the global "sName" through the statement:

global sName

But when I go to use the variable it still gives me an error:

NameError: global name 'sName' is not defined

I thought perhaps I need to indicate 'globality' in my main module, so
before I initiallized sName in doStuff.py I added:

global sName

But it doesn't help me. I had this issue before and resolved it by
declaring the variable global in the sub-module utility.py, but then I
needed to reference it in my main module with a prefix:

utility.sName = ""

It's more verbose,and defining globals in a submodule seems backward.
But also, what if I need to access "sName" in another imported module,
say "otherstuff.py"? I would do my "import otherstuff" call in my main
module, but would I have to put an "import utility" into the
otherstuff.py file?

Is there some way I can define globals in my main module, and have them
accessible in all my imported submodule?

As you can see I'm a little unsure about the global handling in a
multi-module environment. Any suggestions appreciated. I've read
http://docs.python.org/ref/naming.html but it hasn't enlightened me on
this one.

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  • Fredrik Lundh at Aug 27, 2008 at 9:08 pm

    RgeeK wrote:

    I have a main module doStuff.py and another module utility.py. At the
    start of doStuff.py I call

    import utility.py
    that tries to import a module named "py" from the package "utility".
    Then I also proceed to initiallize some global variables

    sName = ""
    Within my utility.py file, I define the makeOne function. But I want to
    use that same global variable "sName" In utility.py I have tried to
    indicate that I'm using the global "sName" through the statement:

    global sName
    the "global" directive in Python is used *inside* a function or method
    to indicate that a given name is not local.

    Python doesn't have "program-wide global" variables; if you need that,
    create a support module and import that module everywhere you need to
    access those variables:

    # file: globalvars.py
    sName = ""

    # file: myprogram.py
    import globalvars
    print globalvars.sName

    etc.

    </F>
  • Rgg at Aug 28, 2008 at 1:47 am

    Fredrik Lundh wrote:
    import utility.py
    that tries to import a module named "py" from the package "utility".
    oops - that was just a typo in my post - I meant of course "import utility"
    Python doesn't have "program-wide global" variables; if you need that,
    create a support module and import that module everywhere you need to
    access those variables:

    # file: globalvars.py
    sName = ""

    # file: myprogram.py
    import globalvars
    print globalvars.sName

    etc.

    </F>
    That's news - thanks, I didn't realize that there just wasn't the
    concept of program-wide globals. The support module idea sounds like a
    path forward.

    -R.
  • RgeeK at Aug 28, 2008 at 1:49 am

    Fredrik Lundh wrote:
    import utility.py
    that tries to import a module named "py" from the package "utility".
    oops - that was just a typo in my post - I meant of course "import utility"
    >
    Python doesn't have "program-wide global" variables; if you need that,
    create a support module and import that module everywhere you need to
    access those variables: >
    # file: globalvars.py
    sName = "" >
    # file: myprogram.py
    import globalvars
    print globalvars.sName >
    etc. >
    </F>
    >

    That's news - thanks, I didn't realize that there just wasn't the
    concept of program-wide globals. The support module idea sounds like a
    path forward.

    -R.
  • RgeeK at Aug 28, 2008 at 1:51 am

    Dennis Lee Bieber wrote:
    On Wed, 27 Aug 2008 16:21:03 -0400, RgeeK <Ross at no.thanks.spammers>
    declaimed the following in comp.lang.python:
    I have a main module doStuff.py and another module utility.py. At the
    start of doStuff.py I call

    import utility.py
    I hope not... import utility no .py
    Then I also proceed to initiallize some global variables
    Python does not have global variables. Names belong within a module
    (or within functions defined within the module).
    sName = ""

    Then I create a class, some methods etc. In one of the methods I assign
    a value to my variable sName. Then I call a function from within
    my utility.py file:

    utility.makeOne(stuff)


    Within my utility.py file, I define the makeOne function. But I want to
    use that same global variable "sName" In utility.py I have tried to
    indicate that I'm using the global "sName" through the statement:

    global sName
    The global statement is only used within functions (def blocks) to
    indicate that "writes" to the specified name are to modify the MODULE
    level version of the name, otherwise a write modifies a function local
    version of the name (you don't need global for read-only access of
    names, the search for names first looks inside the function, then out to
    the module)
    But when I go to use the variable it still gives me an error:

    NameError: global name 'sName' is not defined

    I thought perhaps I need to indicate 'globality' in my main module, so
    before I initiallized sName in doStuff.py I added:

    global sName

    But it doesn't help me. I had this issue before and resolved it by
    declaring the variable global in the sub-module utility.py, but then I
    needed to reference it in my main module with a prefix:

    utility.sName = ""

    It's more verbose,and defining globals in a submodule seems backward.
    But also, what if I need to access "sName" in another imported module,
    say "otherstuff.py"? I would do my "import otherstuff" call in my main
    module, but would I have to put an "import utility" into the
    otherstuff.py file?
    If you really need "globals" the common solution is to create a
    module such as "myglobals", define all the shared names within that
    module, and import that module where ever you need access to one of the
    names. And yes, you will need to qualify all those names with the module
    name (though you can do things like:

    import myglobals as mg

    and then use

    mg.somename

    instead of

    myglobals.somename)

    Thanks for the reply. Good to see that approach has broad support :)
    I'll do that. I like the idea of a nice short alias for the import to
    keep the qualifications brief.

    Ross.

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postedAug 27, '08 at 8:21p
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