IDLE being too clever checking nonlocal declarations?

[Steven D'Aprano]

On Mon, 21 Oct 2013 23:26:28 -0400, Terry Reedy wrote:

> On 10/21/2013 7:52 PM, Steven D'Aprano wrote:
>> On Mon, 21 Oct 2013 15:51:56 -0400, Terry Reedy wrote:
>>
>>> On 10/21/2013 11:06 AM, Chris Angelico wrote:
>>>> Try typing this into IDLE:
>>>>
>>>>>>> def a():
>>>>       def b():
>>>>           nonlocal q
>>>> SyntaxError: no binding for nonlocal 'q' found
>>>
>>> If you submit those three lines to Python from the command line, that
>>> is what you see.
>>
>> Arguably, that's also too strict,
> 
> As I quoted from the doc, it is an error for a program to contain a
> nonlocal with no referent. The reason is one only needs nonlocal to bind
> and unlike with 'global newname', it would be undefined where to do the
> binding.

Yep, I got that, but what I'm saying is that it is too strict to raise 
the exception at the point where it sees "nonlocal q". The CPython 
interpreter allows q to be defined inside function a but after function 
b, e.g. this is allowed:

def a():
    def b():
        nonlocal q
        q += 1
    q = 2  # <=======


If IDLE and the code.py module requires q to be strictly defined before 
function b, then it is too strict. Your analysis of the bug as being in 
code.py seems plausible.



>> [steve at ando ~]$ python3.3 -c "def a():
>>>      def b():
>>>          nonlocal q
>>>      q = 1
>>> "
> 
> What system lets you do that? (See other thread about Windows not
> allowing that, because newline terminates the command even after ".) Is
> '>' a line continuation marker (like '...' in Python)?

Yes, sorry I should have said. That's bash, under Linux.

Here's another way:


steve at runes:~$ python3.3 -c "def a():^M  def b():^M    nonlocal q^M  
q=1^Mprint(a() is None)"
True


Still bash under Linux (a different machine), the ^M is *not* a pair of 
characters ^ followed by M but an actually newline, generated by typing 
Ctrl-V Enter (that's the ENTER key, not the letters E n t e r).

In theory I should be able to get something working with \n escapes 
instead of ^M, but I can't get it working. But I'm not an expect at bash's 
arcane rules for quoting and escaping special characters.



-- 
Steven