mrocklin: +1 from me
diff --git a/dask/delayed.py b/dask/delayed.py
index d54d9b941..a9cbf6360 100644
--- a/dask/delayed.py
+++ b/dask/delayed.py
@@ -240,9 +240,29 @@ def delayed(obj, name=None, pure=False, nout=None, traverse=True):
     >>> res.compute()  # doctest: +SKIP
     AttributeError("'list' object has no attribute 'not_a_real_method'")
 
-    Methods are assumed to be impure by default, meaning that subsequent calls
-    may return different results. To assume purity, set `pure=True`. This
-    allows sharing of any intermediate values.
+    "Magic" methods (e.g. operators and attribute access) are assumed to be
+    pure, meaning that subsequent calls must return the same results.  This is
+    not overrideable. To invoke an impure attribute or operator, you'd need to
+    use it in a delayed function with ``pure=False``.
+
+    >>> class Incrementer(object):
+    ...     def __init__(self):
+    ...         self._n = 0
+    ...     @property
+    ...     def n(self):
+    ...         self._n += 1
+    ...         return self._n
+    ...
+    >>> x = delayed(Incrementer())
+    >>> x.n.key == x.n.key
+    True
+    >>> get_n = delayed(lambda x: x.n, pure=False)
+    >>> get_n(x).key == get_n(x).key
+    False
+
+    In contrast, methods are assumed to be impure by default, meaning that
+    subsequent calls may return different results. To assume purity, set
+    `pure=True`. This allows sharing of any intermediate values.
 
     >>> a.count(2, pure=True).key == a.count(2, pure=True).key
     True
@@ -252,7 +272,6 @@ def delayed(obj, name=None, pure=False, nout=None, traverse=True):
 
     >>> a.count(2, dask_key_name="count_2")
     Delayed("count_2")
-
     """
     if isinstance(obj, Delayed):
         return obj
@@ -346,7 +365,7 @@ class Delayed(base.Base):
     def __getattr__(self, attr):
         if attr.startswith('_'):
             raise AttributeError("Attribute {0} not found".format(attr))
-        return DelayedAttr(self, attr, 'getattr-%s' % tokenize(self, attr))
+        return DelayedAttr(self, attr)
 
     def __setattr__(self, attr, val):
         if attr in self.__slots__:
@@ -436,10 +455,10 @@ class DelayedLeaf(Delayed):
 class DelayedAttr(Delayed):
     __slots__ = ('_obj', '_attr', '_key')
 
-    def __init__(self, obj, attr, key):
+    def __init__(self, obj, attr):
         self._obj = obj
         self._attr = attr
-        self._key = key
+        self._key = 'getattr-%s' % tokenize(obj, attr, pure=True)
 
     @property
     def dask(self):

Inheritance of Purity
(As discussed here: http://stackoverflow.com/questions/42773134/inheritance-of-purity/42773643)

I have a question about inheritance of function purity. For example, consider this case:

```python
In [1]: from dask import delayed

In [2]: myArr = delayed(np.ones, pure=True)((10,10))

In [3]: myArr
Out[3]: Delayed('ones-850ff41a84b309775d01d5f3e5c4d1c4')

In [4]: myArr = delayed(np.ones, pure=True)((10,10))

In [5]: myArr
Out[5]: Delayed('ones-850ff41a84b309775d01d5f3e5c4d1c4')

In [6]: myArr.shape
Out[6]: Delayed('getattr-de14f312-2605-4fc4-a419-c376520f73b4')

In [7]: myArr.shape
Out[7]: Delayed('getattr-9e547a62-0bc6-43e5-8d3c-cac532b73511')

In [8]: delayed(getattr, pure=True)(myArr, 'shape')
Out[8]: Delayed('getattr-5224be928bad33c9778d4f96d610cc37')

In [9]: delayed(getattr, pure=True)(myArr, 'shape')
Out[9]: Delayed('getattr-5224be928bad33c9778d4f96d610cc37')

```

I would expect line [6] and [7] to yield the same key, since they are accessing an attribute from a delayed instance declared pure. However, it is not the case, and I must explicitly declare the `getattr` method to be pure for this to work, as seen in lines [8] and [9].

As discussed in the stackoverflow link, this seems to be purely an issue of `dask` semantics. I would be inclined to voting for purity to be inherited. But I am a new user, so I would appreciate feedback/comments on this. Thanks!

PS: The eventual use case is for dask distributed. It seems that the way purity is treated in this case may possibly be different than the case listed here.
diff --git a/dask/tests/test_delayed.py b/dask/tests/test_delayed.py
index 11f00a428..bfea68244 100644
--- a/dask/tests/test_delayed.py
+++ b/dask/tests/test_delayed.py
@@ -69,6 +69,7 @@ def test_methods():
 
 def test_attributes():
     a = delayed(2 + 1j)
+    assert a.real._key == a.real._key
     assert a.real.compute() == 2
     assert a.imag.compute() == 1
     assert (a.real + a.imag).compute() == 3

pip install -e .[complete]
parse_log_pytest
pytest
pytest flake8 pandas_datareader pytest-xdist
apt-get update apt-get install -y gcc
3.6
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
aiobotocore==2.1.2
aiohttp==3.8.6
aioitertools==0.11.0
aiosignal==1.2.0
async-timeout==4.0.2
asynctest==0.13.0
attrs @ file:///opt/conda/conda-bld/attrs_1642510447205/work
botocore==1.23.24
certifi==2021.5.30
charset-normalizer==2.0.12
click==8.0.4
cloudpickle==2.2.1
-e git+https://github.com/dask/dask.git@0c39da3493891891830ab9e8eb5d5d8db203f826#egg=dask
distributed==1.16.1
execnet==1.9.0
flake8==5.0.4
frozenlist==1.2.0
fsspec==2022.1.0
HeapDict==1.0.1
idna==3.10
idna-ssl==1.1.0
importlib-metadata==4.2.0
iniconfig @ file:///home/linux1/recipes/ci/iniconfig_1610983019677/work
jmespath==0.10.0
locket==1.0.0
lxml==5.3.1
mccabe==0.7.0
more-itertools @ file:///tmp/build/80754af9/more-itertools_1637733554872/work
msgpack-python==0.5.6
multidict==5.2.0
numpy==1.19.5
packaging @ file:///tmp/build/80754af9/packaging_1637314298585/work
pandas==1.1.5
pandas-datareader==0.10.0
partd==1.2.0
pluggy @ file:///tmp/build/80754af9/pluggy_1615976315926/work
psutil==7.0.0
py @ file:///opt/conda/conda-bld/py_1644396412707/work
pycodestyle==2.9.1
pyflakes==2.5.0
pyparsing @ file:///tmp/build/80754af9/pyparsing_1635766073266/work
pytest==6.2.4
pytest-xdist==3.0.2
python-dateutil==2.9.0.post0
pytz==2025.2
requests==2.27.1
s3fs==2022.1.0
six==1.17.0
sortedcollections==2.1.0
sortedcontainers==2.4.0
tblib==1.7.0
toml @ file:///tmp/build/80754af9/toml_1616166611790/work
toolz==0.12.0
tornado==6.1
typing_extensions @ file:///opt/conda/conda-bld/typing_extensions_1647553014482/work
urllib3==1.26.20
wrapt==1.16.0
yarl==1.7.2
zict==2.1.0
zipp @ file:///tmp/build/80754af9/zipp_1633618647012/work

name: dask
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - attrs=21.4.0=pyhd3eb1b0_0
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - importlib_metadata=4.8.1=hd3eb1b0_0
  - iniconfig=1.1.1=pyhd3eb1b0_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - more-itertools=8.12.0=pyhd3eb1b0_0
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - packaging=21.3=pyhd3eb1b0_0
  - pip=21.2.2=py36h06a4308_0
  - pluggy=0.13.1=py36h06a4308_0
  - py=1.11.0=pyhd3eb1b0_0
  - pyparsing=3.0.4=pyhd3eb1b0_0
  - pytest=6.2.4=py36h06a4308_2
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - toml=0.10.2=pyhd3eb1b0_0
  - typing_extensions=4.1.1=pyh06a4308_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zipp=3.6.0=pyhd3eb1b0_0
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - aiobotocore==2.1.2
      - aiohttp==3.8.6
      - aioitertools==0.11.0
      - aiosignal==1.2.0
      - async-timeout==4.0.2
      - asynctest==0.13.0
      - botocore==1.23.24
      - charset-normalizer==2.0.12
      - click==8.0.4
      - cloudpickle==2.2.1
      - distributed==1.16.1
      - execnet==1.9.0
      - flake8==5.0.4
      - frozenlist==1.2.0
      - fsspec==2022.1.0
      - heapdict==1.0.1
      - idna==3.10
      - idna-ssl==1.1.0
      - importlib-metadata==4.2.0
      - jmespath==0.10.0
      - locket==1.0.0
      - lxml==5.3.1
      - mccabe==0.7.0
      - msgpack-python==0.5.6
      - multidict==5.2.0
      - numpy==1.19.5
      - pandas==1.1.5
      - pandas-datareader==0.10.0
      - partd==1.2.0
      - psutil==7.0.0
      - pycodestyle==2.9.1
      - pyflakes==2.5.0
      - pytest-xdist==3.0.2
      - python-dateutil==2.9.0.post0
      - pytz==2025.2
      - requests==2.27.1
      - s3fs==2022.1.0
      - six==1.17.0
      - sortedcollections==2.1.0
      - sortedcontainers==2.4.0
      - tblib==1.7.0
      - toolz==0.12.0
      - tornado==6.1
      - urllib3==1.26.20
      - wrapt==1.16.0
      - yarl==1.7.2
      - zict==2.1.0
prefix: /opt/conda/envs/dask

dask/tests/test_delayed.py::test_attributes
dask/tests/test_delayed.py::test_to_task_dask dask/tests/test_delayed.py::test_delayed dask/tests/test_delayed.py::test_operators dask/tests/test_delayed.py::test_methods dask/tests/test_delayed.py::test_method_getattr_optimize dask/tests/test_delayed.py::test_delayed_errors dask/tests/test_delayed.py::test_common_subexpressions dask/tests/test_delayed.py::test_lists dask/tests/test_delayed.py::test_literates dask/tests/test_delayed.py::test_literates_keys dask/tests/test_delayed.py::test_lists_are_concrete dask/tests/test_delayed.py::test_traverse_false dask/tests/test_delayed.py::test_pure dask/tests/test_delayed.py::test_nout dask/tests/test_delayed.py::test_kwargs dask/tests/test_delayed.py::test_array_delayed dask/tests/test_delayed.py::test_array_bag_delayed dask/tests/test_delayed.py::test_delayed_picklable dask/tests/test_delayed.py::test_delayed_compute_forward_kwargs dask/tests/test_delayed.py::test_delayed_method_descriptor dask/tests/test_delayed.py::test_delayed_callable dask/tests/test_delayed.py::test_delayed_name_on_call dask/tests/test_delayed.py::test_callable_obj dask/tests/test_delayed.py::test_name_consitent_across_instances dask/tests/test_delayed.py::test_sensitive_to_partials dask/tests/test_delayed.py::test_delayed_name dask/tests/test_delayed.py::test_finalize_name
dask/delayed.py
dask/delayed.py