[Python-Dev] Is implicit underscore assignment buggy?

Raymond Hettinger raymond.hettinger at verizon.net
Thu Jun 8 00:35:58 CEST 2006

> 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 _.

BTW, there is a trivial exception to the "most recently printed result" rule.

    >>> 13
    >>> _ = None
    >>> _                   # _ is no longer the most recently printed result


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