[Python-Dev] Is implicit underscore assignment buggy?
jeremy at alum.mit.edu
Thu Jun 8 00:49:38 CEST 2006
On 6/7/06, Raymond Hettinger <raymond.hettinger at verizon.net> wrote:
> > for users, it's actually quite simple to figure out what's in the _
> > variable: it's the most recently *printed* result. if you cannot see
> > it, it's not in there.
> Of course, there's a pattern to it. The question is whether it is the *right*
> behavior. Would the underscore assignment be more useful and intuitive
> if it always contained the immediately preceding result, even if it was None?
> In some cases (such as the regexp example), None is a valid and useful
> possible result of a computation and you may want to access that result with _.
If you're using _ in an interactive environment, it's usually because
you don't want to re-type the value of the expression. If the value
is None, it isn't hard to type.
> BTW, there is a trivial exception to the "most recently printed result" rule.
> >>> 13
> >>> _ = None
> >>> _ # _ is no longer the most recently printed result
If you want to assign to _, the results are your own fault.
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