Hi Anthony,
Thanks for the pointer. I took each variable in turn and fed it through
return dict(foo = variable1)
ran & check for hang
return dict(foo = variable2)
ran & check for hang...
Narrowed it down to 3 lists of tuples.
In all cases the view code was:
{{=BEAUTIFY(foo)}}
for most variables, no problem. For the 3 lists of tuples, hang the server.
Then I eliminated the BEAUTIFY function, and just made a loop in the view:
{{ for items in foo:}}
{{ =items}}
{{pass}}
This worked. No hang. So it has nothing to do with return locals(), but
seems to be BEAUTIFY specifically with these lists.
Finally, in the controller I made a loop to copy the list item by item into
a new list, and return that to BEAUTIFY:
tmp = []
for items in variable1:
tmp.append(items)
return dict(foo=tmp)
On the silly thought that it might clean up whatever data structure was
there. It didn't. Still had the hang.
At this point I would have to crack open the BEAUTIFY function and trace
through it, and honestly I don't even know where to begin. I have put
enough time into this to pretty much rule out the code and the variables I
have. The debuggers show this as a list of 3 tuples. When I use the item
loop in view, it shows a simple list of 3 tuples. It just isn't that
complex of a data structure to be giving me so much headache. In fact, here
it is:
(1L, 0.23359594244831011) (2L, 1.600167232663812e-05) (3L,
1.3562750608171854e-10)
This is so frustrating - so I put that exact list into a variable and
passed it to BEAUTIFY. Of course that worked:
tmp =[(1L, 0.23359594244831011), (2L, 1.600167232663812e-05), (3L,
1.3562750608171854e-10)]
return dict(foo=tmp)
Directly passing the exact list works with BEAUTIFY, it works if I iterate
through the items in the view. Can't break it. For some reason the
function that generates the list creates it in a way that has no visible
problem, works when I iterate through the list, looks fine in the debugger,
but does not work with BEAUTIFY.
A hang is pretty serious, but this is getting beyond my ability to debug. I
really wouldn't know where to start digging into BEAUTIFY, underlying
memory, or exceptions gone wrong...Also given that I am having a general
memory leak on El Capitan, and nobody else is complaining about such a
hang, it smells like a problem on my OS interacting with BEAUTIFY.
On Saturday, July 2, 2016 at 8:06:31 AM UTC-7, Anthony wrote:
>
> Note that locals() is a dictionary including all objects defined in the
> local scope (i.e., your controller function). Perhaps something else in
> locals() is causing the problem. Maybe trying returning an explicitly
> constructed dictionary instead:
>
> return dict(bob=bob)
>
> Otherwise, without seeing your code or having a way to replicate, it is
> difficult to help. You might try doing some inspection of what exactly is
> being fed to BEAUTIFY. In general, a list of tuples should be no problem,
> and how that list of tuples was generated (e.g., via sorted or otherwise)
> should not matter.
>
> Anthony
>
> On Saturday, July 2, 2016 at 2:02:45 AM UTC-4, DNeuman wrote:
>>
>> I have attempted creating a test app a few times. I have spent a week on
>> this so far, with no real progress. Nothing seems to trigger the problem
>> other than the full app.
>>
>> It seems very strange that passing local variables to BEAUTIFY as a list
>> of tuples works in a small app. Yet when the same list of tuples is
>> generated from sorted() it does not work. I even tried putting a sorted()
>> function on a dict in a test app, and it worked with a small app, but not
>> the full app. Very flakey.
>>
>> Is BEAUTIFY and return locals() meant to work with a list of tuples? If
>> not, I'll just rewrite this. I thought it might work, but currently its
>> behavior is unpredictable. Sorry I don't have more details. If I am trying
>> to do something web2py wasn't meant to do, that would help me at least.
>> Please let me know.
>>
>> Thanks,
>>
>> On Saturday, June 18, 2016 at 9:08:50 PM UTC-7, Anthony wrote:
>>>
>>> Probably something else is going on. I suggest you create a minimal app
>>> that reproduces the problem and post it.
>>>
>>> Anthony
>>>
>>> On Saturday, June 18, 2016 at 8:47:42 AM UTC-4, DNeuman wrote:
>>>>
>>>> Hi - first time posting here! First let me say thanks to Professor Di
>>>> Pierro and all the people who have done a great job on Web2Py. I am new to
>>>> web development, and Python, so I really appreciate all the work you did
>>>> to
>>>> make this subject approachable. Now for my question:
>>>>
>>>> I am having some difficulty passing a list of tuples from a controller
>>>> using 'return locals()' sometimes it hangs the web2py server.
>>>>
>>>> I have spent a week narrowing this down, and here is what I have; some
>>>> works, some does not...
>>>>
>>>> If I create a simple list named bob = [(2L, 0.2075327747768832), (16L,
>>>> 0.19108106970048253), (3L, 0.13288897732583363), (15L,
>>>> 0.11511204575971237), (12L, 0.10369170755981243), (7L,
>>>> 0.1033849215142939),
>>>> (8L, 0.0957849868092478), (5L, 0.05052350890092832)]
>>>>
>>>> then return locals() I can see this in response._vars in the debugger
>>>> and {{=BEAUTIFY(response._vars)}} works fine. (thats good)
>>>>
>>>>
>>>> However, if I create the same exact list as an output of a sorting
>>>> operation from a dictionary, it hangs the web2py server when I use return
>>>> locals() and {{=BEAUTIFY(response._vars)}} (but only sometimes)
>>>>
>>>>
>>>> Here is what the code is used to generate the sorted list:
>>>>
>>>> def make_list():
>>>> from operator import itemgetter
>>>> #dbg.set_trace() # stop here!
>>>>
>>>> test_dict ={}
>>>>
>>>> test_dict[2L] = 0.773
>>>> test_dict[5L] = 0.003
>>>> test_dict[1L] = 0.31
>>>> test_dict[9L] = 0.0402
>>>> test_dict[12L] = 0.12
>>>> test_dict[7L] = 0.214
>>>>
>>>> test_list = sorted(test_dict.iteritems(), key=itemgetter(1),
>>>> reverse=True)
>>>>
>>>> return test_list #this should be a list of tuples
>>>> [(x,y),(w,z)...()]
>>>>
>>>>
>>>> But here is the weird part - if I have this test case standalone, it
>>>> always works. If I use sorted() in a larger program, it exhibits the hang.
>>>> Very consistent. standalone test = no problem. larger problem = broken.
>>>>
>>>> More about the server hang:
>>>>
>>>> passing bob through locals() causes a hang, whether BEAUTIFY(bob) or
>>>> BEAUTIFY(response._vars) as long as bob is generated from the sorted()
>>>> function. Never hangs when generated from simply creating a list of tuples.
>>>>
>>>>
>>>> passing bob through locals() doesn’t hang unless BEAUTIFY(bob). So, if
>>>> I don't use bob in the view, it doesn't hang. There is something about
>>>> passing this through locals, AND using BEAUTIFY AND creating the list from
>>>> sorted() AND being in a larger program.
>>>>
>>>>
>>>> making bob from sorted() in a large program = hang:
>>>>
>>>> use return locals() and BEAUTIFY(response._vars) -- hang
>>>>
>>>> use return locals() and BEAUTIFY(bob) -- hang
>>>>
>>>>
>>>> works:
>>>>
>>>> return locals() and BEAUTIFY(qlist)
>>>> -- no hang; qlist is some other variable
>>>>
>>>> return locals() and use view {{=bob[0] =bob[1] =bob[2] }}
>>>> -- no hang; here I simply don't use BEAUTIFY and it all works
>>>>
>>>> bob created without using sorted()
>>>> -- no hang; can do whatever I like and it works.
>>>>
>>>>
>>>>
>>>> So I can only guess that I am using sorted() wrong, or using BEAUTIFY
>>>> wrong, or there is some very mysterious aspect of the list that is not
>>>> visible in the debugger which is confusing BEAUTIFY.
>>>>
>>>>
>>>> when I examine response._vars in cases where there is a hang it is
>>>> identical to cases where there is no hang.
>>>>
>>>>
>>>> details:
>>>>
>>>> Mac OS X El Capitan 10.11.5
>>>>
>>>> Web2py 2.14.2-stable+timestamp.2016.03.24.22.47.49
>>>>
>>>> modules installed: numpy
>>>>
>>>> browser: Safari
>>>>
>>>>
>>>> Much appreciate any pointers here! Thanks.
>>>>
>>>>
--
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
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