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[Python-ideas] Syntax for key-value iteration over mappings
Petr Viktorinencukou at gmail.com
Tue Jul 28 19:39:49 CEST 2015
On Mon, Jul 27, 2015 at 1:42 PM, Lennart Regebro <regebro at gmail.com> wrote:> On Mon, Jul 27, 2015 at 4:12 AM, Steven D'Aprano <steve at pearwood.info> wrote:>> It's one more special case syntax for beginners to learn. And it really>> is a special case: there's nothing about "for k:v in iterable" that>> tells you that iterable must have an items() method. You have to>> memorise that fact.>> This I think is a strong argument.>> What error would you get when it's the wrong type? An attribute error> on .items(), or a special SyntaxError "This syntax can only be used on> mappings".> Both are quite incomprehensible unless you know exactly what is going> on and that this is a shortcut for "fox x,y in foo.items():"I think that should be "TypeError: 'foo' object is not a mapping" –similarly to:>>> for x in 123:... pass...Traceback (most recent call last): File "<stdin>", line 1, in <module>TypeError: 'int' object is not iterable
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