The python list mysteriously gets something in my django / piston handler

Question

Note: (I updated this from the first two sentences ... you can view the old post in txt form here: http://bennyland.com/old-2554127.txt ). The update I did was to better understand what was going wrong - and now I at least know what is going on, but I don’t know how to fix it.

Anyway, using Django and Piston, I created a new BaseHandler class called BaseApiHandler that does most of the work that I did in all of my handlers. This worked great until I added the ability to limit the filters applied to my results (for example, "give me only the first result").

Examples (I had to delete ":" because I can not send more URLs): - http // localhost / api / hours_detail / empid / 22 gives me all hours_detail lines from employee # 22 - http // localhost / api / hours_detail / empid / 22 / limit / first gives me the first line hours_detail from employee # 22

What happens when I start / limit / first several times in a row, the first example is interrupted, pretending to be / limit / url when it is not.

Currently, I save whether this restriction is limited and what the limit is in the new class - before this stackoverflow edit, I just used a list with two entries (limit = [] during initialization, limit = [0,1] during installation). Prior to this stackoverflow edit, once you spam / limit / first, when you go to the first example, "limit" will be pre-set to [0,1], and then the handler will limit the request because of this. With the added debugging data, I can confidently say that the list was pre-installed and was not installed at runtime.

I am adding debugging information to my answer so that I can see what is happening. Right now, the first time you request the URL of Example 1, you get this CORRECT statusmsg response:

"statusmsg": "2 hours_detail found with query: {'empid':'22','datestamp':'2009-03-02',}",

URL- 2, CORRECT statusmsg:

"statusmsg": "1 hours_detail found with query: {'empid':'22','datestamp':'2009-03-02','limit','first',with limit[0,1](limit,None... limit set 1 times),}",

, , ( - , , - )

"statusmsg": "1 hours_detail found with query: {'empid':'22','datestamp':'2009-03-02','limit','first',with limit[0,1](limit,None... limit set 10 times),}",

"1 ", URL- 1. , 1, . ( , "limit" : "first" kwarg, islimit 8 10):

"statusmsg": "1 hours_detail found with query: {'empid':'22','datestamp':'2009-03-02',with limit[0,1](limit,None... limit set 10 times),}",
"statusmsg": "1 hours_detail found with query: {'empid':'22','datestamp':'2009-03-02',with limit[0,1](limit,None... limit set 8 times),}",
"statusmsg": "1 hours_detail found with query: {'empid':'22','datestamp':'2009-03-02',with limit[0,1](limit,None... limit set 9 times),}",

, , . , "" , , "limit" , 2 url, [0,1] .

(, : bennyland.com/old-2554127.txt)

URLS.PY - 'urlpatterns = patterns ('

    #hours_detail/id/{id}/empid/{empid}/projid/{projid}/datestamp/{datestamp}/daterange/{fromdate}to{todate}
    #empid is required
    url(r'^api/hours_detail/(?:' + \
        r'(?:[/]?id/(?P<id>\d+))?' + \
        r'(?:[/]?empid/(?P<empid>\d+))?' + \
        r'(?:[/]?projid/(?P<projid>\d+))?' + \
        r'(?:[/]?datestamp/(?P<datestamp>\d{4,}[-/\.]\d{2,}[-/\.]\d{2,}))?' + \
        r'(?:[/]?daterange/(?P<daterange>(?:\d{4,}[-/\.]\d{2,}[-/\.]\d{2,})(?:to|/-)(?:\d{4,}[-/\.]\d{2,}[-/\.]\d{2,})))?' + \
        r')+' + \
        r'(?:/limit/(?P<limit>(?:first|last)))?' + \
        r'(?:/(?P<exact>exact))?$', hours_detail_resource),

HANDLERS.PY

class ResponseLimit(object):
    def __init__(self):
        self._min = 0
        self._max = 0
        self._islimit = 0

    @property
    def min(self):
        if self.islimit == 0:
            raise LookupError("trying to access min when no limit has been set")
        return self._min

    @property
    def max(self):
        if self.islimit == 0:
            raise LookupError("trying to access max when no limit has been set")
        return self._max

    @property
    def islimit(self):
        return self._islimit

    def setlimit(self, min, max):
        self._min = min
        self._max = max
        # incrementing _islimit instead of using a bool so I can try and see why it broken
        self._islimit += 1

class BaseApiHandler(BaseHandler):
    limit = ResponseLimit()
    def __init__(self):
        self._post_name = 'base'

    @property
    def post_name(self):
        return self._post_name

    @post_name.setter
    def post_name(self, value):
        self._post_name = value

    def process_kwarg_read(self, key, value, d_post, b_exact):
        """
        this should be overridden in the derived classes to process kwargs
        """
        pass

    # override 'read' so we can better handle our api searching capabilities
    def read(self, request, *args, **kwargs):
        d_post = {'status':0,'statusmsg':'Nothing Happened'}
        try:
            # setup the named response object
            # select all employees then filter - querysets are lazy in django
            # the actual query is only done once data is needed, so this may
            # seem like some memory hog slow beast, but it actually not.
            d_post[self.post_name] = self.queryset(request)
            s_query = ''

            b_exact = False
            if 'exact' in kwargs and kwargs['exact'] <> None:
                b_exact = True
                s_query = '\'exact\':True,'

            for key,value in kwargs.iteritems():
                # the regex url possibilities will push None into the kwargs dictionary
                # if not specified, so just continue looping through if that the case
                if value is None or key == 'exact':
                    continue

                # write to the s_query string so we have a nice error message
                s_query = '%s\'%s\':\'%s\',' % (s_query, key, value)

                # now process this key/value kwarg
                self.process_kwarg_read(key=key, value=value, d_post=d_post, b_exact=b_exact)

            # end of the kwargs for loop
            else:
                if self.limit.islimit > 0:
                    s_query = '%swith limit[%s,%s](limit,%s... limit set %s times),' % (s_query, self.limit.min, self.limit.max, kwargs['limit'],self.limit.islimit)
                    d_post[self.post_name] = d_post[self.post_name][self.limit.min:self.limit.max]
                if d_post[self.post_name].count() == 0:
                    d_post['status'] = 0
                    d_post['statusmsg'] = '%s not found with query: {%s}' % (self.post_name, s_query)
                else:
                    d_post['status'] = 1
                    d_post['statusmsg'] = '%s %s found with query: {%s}' % (d_post[self.post_name].count(), self.post_name, s_query)
        except:
            e = sys.exc_info()[1]
            d_post['status'] = 0
            d_post['statusmsg'] = 'error: %s %s' % (e, traceback.format_exc())
            d_post[self.post_name] = []

        return d_post


class HoursDetailHandler(BaseApiHandler):
    #allowed_methods = ('GET', 'PUT', 'POST', 'DELETE',)
    model = HoursDetail
    exclude = ()

    def __init__(self):
        BaseApiHandler.__init__(self)
        self._post_name = 'hours_detail'

    def process_kwarg_read(self, key, value, d_post, b_exact):
        # each query is handled slightly differently... when keys are added
        # handle them in here.  python doesn't have switch statements, this
        # could theoretically be performed using a dictionary with lambda
        # expressions, however I was affraid it would mess with the way the
        # filters on the queryset work so I went for the less exciting
        # if/elif block instead

        # querying on a specific row
        if key == 'id':
            d_post[self.post_name] = d_post[self.post_name].filter(pk=value)

        # filter based on employee id - this is guaranteed to happen once
        # per query (see read(...))
        elif key == 'empid':
            d_post[self.post_name] = d_post[self.post_name].filter(emp__id__exact=value)

        # look for a specific project by id
        elif key == 'projid':
            d_post[self.post_name] = d_post[self.post_name].filter(proj__id__exact=value)

        elif key == 'datestamp' or key == 'daterange':
            d_from = None
            d_to = None
            # first, regex out the times in the case of range vs stamp
            if key == 'daterange':
                m = re.match('(?P<daterangefrom>\d{4,}[-/\.]\d{2,}[-/\.]\d{2,})(?:to|/-)(?P<daterangeto>\d{4,}[-/\.]\d{2,}[-/\.]\d{2,})', \
                             value)
                d_from = datetime.strptime(m.group('daterangefrom'), '%Y-%m-%d')
                d_to = datetime.strptime(m.group('daterangeto'), '%Y-%m-%d')
            else:
                d_from = datetime.strptime(value, '%Y-%m-%d')
                d_to = datetime.strptime(value, '%Y-%m-%d')

            # now min/max to get midnight on day1 through just before midnight on day2
            # note: this is a hack because as of the writing of this app,
            # __date doesn't yet exist as a queryable field thus any
            # timestamps not at midnight were incorrectly left out
            d_from = datetime.combine(d_from, time.min)
            d_to = datetime.combine(d_to, time.max)

            d_post[self.post_name] = d_post[self.post_name].filter(clock_time__gte=d_from)
            d_post[self.post_name] = d_post[self.post_name].filter(clock_time__lte=d_to)

        elif key == 'limit':
            order_by = 'clock_time'
            if value == 'last':
                order_by = '-clock_time'
            d_post[self.post_name] = d_post[self.post_name].order_by(order_by)
            self.limit.setlimit(0, 1)

        else:
            raise NameError

    def read(self, request, *args, **kwargs):
        # empid is required, so make sure it exists before running BaseApiHandler read method
        if not('empid' in kwargs and kwargs['empid'] <> None and kwargs['empid'] >= 0):
            return {'status':0,'statusmsg':'empid cannot be empty'}
        else:
            return BaseApiHandler.read(self, request, *args, **kwargs)

Answer 1

, , has_limit() True, limit - 2, , :

s_query = '%swith limit[%s,%s](limit,%s > traceback:%s),' % 
          (s_query, self.limit[0], self.limit[1], kwargs['limit'], 
           self.limit[2])

self.limit ? :

if self.has_limit():
    s_query += 'with limit[%s,%s]' % self.limit[0:1]
    if 'limit' in kwargs and len(self.limit) > 2:
        s_query += '(limit,%s > traceback:%s),' % 
              (kwargs['limit'], self.limit[2])

Answer 2

, , get_limit. (, , ) . , get_limit, , del , [:]. :

def get_limit(self): 
    return self._limit[:]

.