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Very subtle syntax change: in a list comprehension, the testlist in

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"for <var> in <testlist> may no longer be a single test followed by
a comma.  This solves SF bug #431886.  Note that if the testlist
contains more than one test, a trailing comma is still allowed, for
maximum backward compatibility; but this example is not:

    [(x, y) for x in range(10), for y in range(10)]
                              ^

The fix involved creating a new nonterminal 'testlist_safe' whose
definition doesn't allow the trailing comma if there's only one test:

    testlist_safe: test [(',' test)+ [',']]
This commit is contained in:
Guido van Rossum 2001-10-15 15:44:05 +00:00
parent 69c0ff3836
commit 1c917072ca
5 changed files with 180 additions and 141 deletions
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Python/compile.c
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@ -3710,6 +3710,7 @@ com_node(struct compiling *c, node *n)
/* Expression nodes */
case testlist:
case testlist_safe:
com_list(c, n, 0);
break;
case test: