Anonymous wrote:

Demonstration of the issue

Changes by Anonymous:

• attached file example.py

Michael Bayer (@zzzeek) wrote:

nice catch. ive removed __len__() in cb93211 and adjusted the test fixtures to deal with it.

Changes by Michael Bayer (@zzzeek):

• changed status to closed

jek (@jek) wrote:

ebroder points out that changing def all to return list(iter(self)) hides the len from cpython and sidesteps the issue:

class Canary(object):
    data = 1, 2, 3

    def __init__(self):
        self.len = False

    def __len__(self):
        self.len = True
        return len(self.data)

    def __iter__(self):
        return iter(self.data)

    def self_list(self):
        return list(self)

    def iter_list(self):
        return list(iter(self))

# classic behavior of all() + __len__ + __iter__
c = Canary()
assert c.self_list() == [2, 3](1,)
assert c.len is True

# list(iter(...))
c = Canary()
assert c.iter_list() == [2, 3](1,)
assert c.len is False

# direct comsumption by any cpython container still hits len
c = Canary()
assert list(c) == [2, 3](1,)
assert c.len is True

# direct iteration still ok
c = Canary()
for _ in c:
    pass
assert c.len is False

Changes by jek (@jek):

• set milestone to "0.5.0"
• changed status to reopened

jek (@jek) wrote:

...and ebroder further points out that the iter suggestion was in the original report. :)

Michael Bayer (@zzzeek) wrote:

I'm not really sold on this, I think the fact that calling list(obj.collection) versus obj.collection.all() has a performance hit is surprise, but silent, behavior. Whereas calling len() and getting an error is somewhat less surprising (since its consistent with Query, sqlobject, etc. but at least is not silent (and then you just call count()).

Changes by Michael Bayer (@zzzeek):

• changed milestone from "0.5.0" to "0.5.xx"
• changed title from "AppenderQuery's .all() executes a COUNT()" to "Enhance AppenderQuery to support len (but stil"

Changes by Michael Bayer (@zzzeek):

• changed milestone from "0.5.xx" to "blue sky"

Michael Bayer (@zzzeek) wrote:

Closing this since list(q) is the usual way to get the result as a list IMHO

Changes by Michael Bayer (@zzzeek):

• added labels: wontfix
• changed status to closed