Python, suds, Error.

Question

When I'm trying get method from remote webservice it gives me error.

My code is:

        portion=10
        start=0
        print self.stamp.datetime
        client=self.client
        while 1:
            print 'getting ids...........'
            fresh_ids=client.service.GetTopicsIDsUpdatedAfterDateTime(self.stamp.datetime,start,portion) #this line makes exception
            if len(fresh_ids) is not 0:
                for id in fresh_ids:
                    yield id
                start=+portion
            else:
                print 'No updated topics anymore'
                sys.exit()

There is trace-back:

 /usr/lib/python2.5/site-packages/suds-0.3.5-py2.5.egg/suds/client.py
in invoke(self, args, kwargs)
    469         binding = self.method.binding.input
    470         binding.options = self.options
--> 471         msg = binding.get_message(self.method, args, kwargs)
    472         timer.stop()
    473         metrics.log.debug(

/usr/lib/python2.5/site-packages/suds-0.3.5-py2.5.egg/suds/bindings/binding.py
in get_message(self, method, args, kwargs)
     96         content = self.headercontent(method)
     97         header = self.header(content)
---> 98         content = self.bodycontent(method, args, kwargs)
     99         body = self.body(content)
    100         env = self.envelope(header, body)

/usr/lib/python2.5/site-packages/suds-0.3.5-py2.5.egg/suds/bindings/rpc.py
in bodycontent(self, method, args, kwargs)
     61             p = self.mkparam(method, pd, value)
     62             if p is not None:
---> 63                 root.append(p)
     64             n += 1
     65         return root

/usr/lib/python2.5/site-packages/suds-0.3.5-py2.5.egg/suds/sax/element.py
in append(self, objects)
    329                 child.parent = self
    330                 continue
--> 331             raise Exception('append %s not-valid' %
child.__class__.__name__)
    332         return self
    333

<type 'exceptions.Exception'>: append list not-valid

There is the method in suds module which raise Exeption:

def insert(self, objects, index=0):
        """
        Insert an L{Element} content at the specified index.
        @param objects: A (single|collection) of attribute(s) or element(s)
            to be added as children.
        @type objects: (L{Element}|L{Attribute})
        @param index: The position in the list of children to insert.
        @type index: int
        @return: self
        @rtype: L{Element}
        """
        objects = (objects,)
        for child in objects:
            if isinstance(child, Element):
                self.children.insert(index, child)
                child.parent = self
            else:
                raise Exception('append %s not-valid' % child.__class__.__name__)
        return self

In console everything is going good. I'm stuck.

Ok i tryied make experimet:

def YieldID(self):
        portion=10
        start=0
        print self.stamp.datetime
        fresh_ids=self.client.service.GetTopicsIDsUpdatedAfterDateTime(self.stamp.datetime,start,portion) #This work
        while 1:
            print 'getting ids...........'
            fresh_ids=self.client.service.GetTopicsIDsUpdatedAfterDateTime(self.stamp.datetime,start,portion) # This raise exception
            if len(fresh_ids)!=0:
                for id in fresh_ids:
                    yield id
                start=+portion
            else:
                print 'No updated topics anymore'
                sys.exit()

I add calling of the same method before WHILE end it work. But when it go inside while gives me exception.

How it can work before loop, and don't work inside loop? That is the main question. What changed?

I tryied even change while to for

Answer 1

Edit: On another look at the code, I noticed that this line:

            start=+portion

needs to be changed to

            start += portion

That might make the following analysis unnecessary... but I think there might still be an issue in your suds source, as explained below.

---

The first question I'd ask is: Are you sure that nothing is changing inside your self.client object between calls to YieldID?

The other concern I have -- which may well be indicative of nothing at all -- is that you may have posted the wrong source for the function where the Exception is raised. The traceback shows that the Exception is raised during a call to append, but the code you included is for insert. It looks as if insert's Exception message identifies it as "append" due to a copy and paste error.

And there's more. Assuming that I've identified the right source location, here's the full source for append, which starts with line number 313:

def append(self, objects):
    """
    Append the specified child based on whether it is an
    element or an attrbuite.
    @param objects: A (single|collection) of attribute(s) or element(s)
        to be added as children.
    @type objects: (L{Element}|L{Attribute})
    @return: self
    @rtype: L{Element}
    """
    if not isinstance(objects, (list, tuple)):
        objects = (objects,)
    for child in objects:
        if isinstance(child, Element):
            self.children.append(child)
            child.parent = self
            continue
        if isinstance(child, Attribute):
            self.attributes.append(child)
            child.parent = self
            continue
        raise Exception('append %s not-valid' % child.__class__.__name__)
    return self

Here, the Exception is raised on line 334, not 331 as your traceback shows.

Are you sure that you're using the original version of suds 0.3.5, and not a modified version? Because the original version of append has an interesting difference with insert: insert always creates a tuple out of its input argument, which seems redundant at best:

def insert(self, objects, index=0): // line 337
    # ... snip to line 348
    objects = (objects,)

whereas the original append does this conditionally (see above):

    if not isinstance(objects, (list, tuple)):
        objects = (objects,)

Now look at the message in the exception:

: append list not-valid

This means that the child that it tried to append was itself a list. But how could this be? If a list had been passed in as input, then we should be iterating through the children of that list... which should not themselves be lists.

Hmm. Perhaps a doubly-nested list had been passed into append as the object parameter, which would seem to indicate some pretty bad corruption of data structures. (See my first question.)

Or...

What follows is sheer speculation, and can't possibly be right ... unless it is...

Or, maybe, you're using a modified version of Suds in which that conditional conversion to a list has been removed, along with the iteration through the list? That would explain the 3-line difference (331 vs. 334) between the code you posted and the source that I found online. Could you double-check the source file that you're using, and let us know for sure?