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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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10
Modules/parsermodule.c
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@ -1039,6 +1039,14 @@ validate_testlist(node *tree)
}
static int
validate_testlist_safe(node *tree)
{
return (validate_repeating_list(tree, testlist_safe,
validate_test, "testlist_safe"));
}
/* '*' NAME [',' '**' NAME] | '**' NAME
*/
static int
@ -1218,7 +1226,7 @@ validate_list_for(node *tree)
res = (validate_name(CHILD(tree, 0), "for")
&& validate_exprlist(CHILD(tree, 1))
&& validate_name(CHILD(tree, 2), "in")
&& validate_testlist(CHILD(tree, 3)));
&& validate_testlist_safe(CHILD(tree, 3)));
return res;
}