Implements sage.misc.misc.inject_variable(name, value)

[nthiery]

From the doc:

    inject a variable into the main global namespace

    INPUT:
     - name  - a string
     - value - anything

    EXAMPLES::

        sage: from sage.misc.misc import inject_variable
        sage: inject_variable("a", 314)
        sage: a
        314

This will be used in the upcoming "inject_shorthands" patch for symmetric functions #7777, and could be used in the various inject_variable code instead of manipulating directly globals() (which could be incorrect if not called directly from the interpreter/notebook.

[nthiery]

(note: patch prepared and tested on 4.2 not 4.3)

[robertwb]

I'd rather it looked for __name__ == '__main__' than wiki_create_instance.

[nthiery]

Replying to robertwb:

I'd rather it looked for __name__ == '__main__' than wiki_create_instance.

Ah, excellent, that sure is the right way for doing this. I had missed this name thing.

Thanks for the suggestion! Patch updated.

[mhansen]

This looks good to me.

[jhpalmieri]

If I do

sage: inject_variable(3, 34)  # pass a non-string to inject_variable, which I probably shouldn't do

then tab-completion is broken. This is odd, and a little alarming. Since this function isn't meant for casual users, maybe this isn't a big deal, but otherwise, perhaps we should check that the first argument is a string.

Here's another question:

sage: from sage.misc.misc import inject_variable
sage: inject_variable('a', 23)
sage: inject_variable('a', 26)
/Applications/sage/local/bin/sage-ipython:1: RuntimeWarning: redefining global value `a`
  #!/usr/bin/env python
sage: inject_variable('a', 29)
sage: inject_variable('a', 33)

Why is the warning only printed the first time? Is that just the nature of these warnings?

[nthiery]

Replying to jhpalmieri:

If I do

sage: inject_variable(3, 34)  # pass a non-string to inject_variable, which I probably shouldn't do

then tab-completion is broken. This is odd, and a little alarming. Since this function isn't meant for casual users, maybe this isn't a big deal, but otherwise, perhaps we should check that the first argument is a string.

Thanks for catching this. Please review the trivial #7928 follow up!

Here's another question:

sage: from sage.misc.misc import inject_variable
sage: inject_variable('a', 23)
sage: inject_variable('a', 26)
/Applications/sage/local/bin/sage-ipython:1: RuntimeWarning: redefining global value `a`
  #!/usr/bin/env python
sage: inject_variable('a', 29)
sage: inject_variable('a', 33)

Why is the warning only printed the first time? Is that just the nature of these warnings?

Ah, I had not noticed this. It seems to be a feature of warn. I added a comment in #7928.