On Mon, 19 Apr 2010 13:09:34 +0200, bb <bblo...@arcor.de> wrote: > Tnx! > > Is there any explanation why the magic ends with del ? > > sage: del x > sage: x > --------------------------------------------------------------------------- > NameError Traceback (most recent call last) > > /home/bb/sage-4.3.5/local/lib/python2.6/site-packages/sage/all_cmdline.pyc > in <module>() > > NameError: name 'x' is not defined > sage: > > > So the feature theses fits like a glove?
A very popular feature is introspection. In this particular case, doing sage: reset? would tell you what reset does: "Delete all user defined variables, reset all globals variables back to their default state, and reset all interfaces to other computer algebra systems." The feature that Harald was referring to is that x is a predefined global variable. You know this by doing sage: globals()['x'] x So now we know what the Sage function "reset" does. "del", on the other hand, is a Python builtin function. Googling "del python" gives that "del can also be used to delete entire variables". So "del x" deletes the global variable from globals(): sage: del x sage: globals()['x'] --------------------------------------------------------------------------- KeyError Traceback (most recent call last) /home/ghitza/<ipython console> in <module>() KeyError: 'x' But if you reset again, x is back: sage: reset sage: globals()['x'] x And everything is behaving exactly as the docstrings indicate. Alex -- Alex Ghitza -- http://aghitza.org/ Lecturer in Mathematics -- The University of Melbourne -- Australia -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
