I think using 'with' keyword can cause some ambiguity. for example I would surely try to write
>>> x = a+b with self: >>> b = member
and using with at the end of block brings more ambiguity:
>>> stmt1() >>> stmt2() >>> with self: >>> member = stmt3()
compare to:
>>> stmt1() >>> stmt2() >>> with: >>> variable = stmt3()
a way different semantics with just one word added/deleted.
Except that for a "with <expr>:" block, attributes of the expression must be preceded by a dot:
Py> stmt1() Py> stmt2() Py> with self: ... .member = stmt3()
The advantages of the 'with' block are that 'self' is only looked up once, and you only need to type it once. The leading dot is still required to disambiguate attribute references from standard name references.
Despite that, I think you are right that the ambiguity is greater than I first thought. Correct code is reasonably easy to distinguish, but in the presence of errors it is likely to be unclear what was intended, which would make life more difficult than it needs to be.
However, I still agree with Alex that the dual life of "where" outside of Python (as an 'additional definitions' clause, as in mathematics, and as a 'conditional' clause, as in SQL), and the varied background of budding Pythoneers is a cause for concern.
'in' is worth considering, as it is already used by Python at least once for declaring use of a namespace (in the 'exec' statement). However, I suspect it would suffer from ambiguity problems similar to those of 'with' (consider "<expr> in <expr>" and "<expr> in: <expr>"). There's also the fact that the statement isn't *really* executed in the inner namespace - any name binding effects are seen in the outer scope, whereas 'exec x in dict' explicitly protects the containing namespace from alteration.
So of the four keywords suggested so far ('where', 'with', 'in', 'using'), I'd currently vote for 'using' with 'where' a fairly close second. My vote goes to 'using' because it has a fairly clear meaning ('execute the statement using this extra information'), and doesn't have the conflicting external baggage that 'where' does.
Cheers, Nick.
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Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
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http://boredomandlaziness.skystorm.net
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