Access to the caller's globals, not your own

[Dan Sommers]

On Mon, 14 Nov 2016 16:20:49 +1100, Steven D'Aprano wrote:

> import library
> SPAMIFY = False  # only affects this module, no other modules
> result = library.make_spam(99)

I must be missing something, because it seems too obvious:

    import library
    # only affects this module, no other modules
    library = library.make_library(spamify=False)
    # ...
    result = library.make_spam(99)

And then in library.py:

    class Library:
        def__init__(self, spamify=False):
            self.spamify = spamify
        def make_spam(self, p):
            return ((p, "spammified")
                    if self.spamify else
                    (p, "hammified"))

    def make_library(spamify=False):
        return Library(spamify)

How do you want the following code to work:

    import library
    SPAMIFY=False

    def make_false_spam():
        return library.make_spam(99)

    def make_true_spam():
        global SPAMIFY
        SPAMIFY=True
        return library.make_spam(99)

I don't have to tell you how many things can go wrong with code like
that.  ;-)

Yes, it's a straw man.  No, I don't think we have all the details of
your use case.  Yes, I'm willing to have missed something subtle (or not
so subtle).

Dan