[Python-Dev] more timely detection of unbound locals

R. David Murray rdmurray at bitdance.com
Tue May 10 15:11:44 CEST 2011

On Tue, 10 May 2011 08:36:38 +0300, Eli Bendersky <eliben at gmail.com> wrote:
> With an unlimited error message length it could make sense to say "Hey, I
> see 'x' may be assigned in this scope, so I mark it local. But this access
> to 'x' happens before assignment - so ERROR". This isn't realistic, of
> course, so I'm wondering:
> 1. Does this error message (although unrealistic) capture all possible
> appearances of UnboundLocalError?
> 2. If the answer to (1) is yes - could it be usefully shortened to be
> clearer than the current "local variable referenced before assignment"?
> This may not be possible, of course, but it doesn't harm trying :-)

How about:

"reference to variable 'y' precedes an assignment that makes it a local

IMO this still leaves room for confusion, but is better because it
indicates the causation more clearly.  (I don't think it is necessary to
capture the subtlety of conditional assignment in the error message.)

R. David Murray           http://www.bitdance.com

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