I wanted to do a survey of various "aggregates" in Python to see if any stand out as making the usual `if stuff: ...` troublesome. I wrote a little script at https://github.com/DavidMertz/LanguagePractice/blob/main/python/aggregates.py.
I'm being deliberately vague about an "aggregate." It might not be a collection strictly speaking, but it is something that might seems to "contain" values in some sense. Basically, I think that standard library and built-in stuff behaves per PEP8. Some other libraries go their own way. I throw in a linked-list implementation I found on PyPI. I've never used it beyond this script; but per what it is, it cannot implement `len()` on O(1) (well, it *could* if it does extra bookkeeping; but then it's kinda a different thing).
In NumPy land, the np.empty vs. np.zeros case is another oddball. On my system, my memory happened to have some prior value that wasn't zero; that could vary between runs, in principle.
These are the results:
Expr: '' | Value: ''
Truth: False | Length: 0
Expr: list() | Value: []
Truth: False | Length: 0
Expr: tuple() | Value: ()
Truth: False | Length: 0
Expr: dict() | Value: {}
Truth: False | Length: 0
Expr: set() | Value: set()
Truth: False | Length: 0
Expr: bytearray() | Value: bytearray(b'')
Truth: False | Length: 0
Expr: bytearray(1) | Value: bytearray(b'\x00')
Truth: True | Length: 1
Expr: bytearray([0]) | Value: bytearray(b'\x00')
Truth: True | Length: 1
Expr: array.array('i') | Value: array('i')
Truth: False | Length: 0
Expr: array.array('i', []) | Value: array('i')
Truth: False | Length: 0
Expr: Nothing() | Value: EmptyNamedTuple()
Truth: False | Length: 0
Expr: deque() | Value: deque([])
Truth: False | Length: 0
Expr: deque([]) | Value: deque([])
Truth: False | Length: 0
Expr: ChainMap() | Value: ChainMap({})
Truth: False | Length: 0
Expr: queue.Queue() | Value: <queue.Queue object at 0x7f0940dd2190>
Truth: True | Length: No length
Expr: asyncio.Queue() | Value: <Queue at 0x7f0940dd2190 maxsize=0>
Truth: True | Length: No length
Expr: multiprocessing.Queue() | Value: <multiprocessing.queues.Queue object at 0x7f0940dd2190>
Truth: True | Length: No length
Expr: np.ndarray(1,) | Value: array([5.e-324])
Truth: True | Length: 1
Expr: np.ndarray((1,0)) | Value: array([], shape=(1, 0), dtype=float64)
Truth: False | Length: 1
Expr: np.empty((1,)) | Value: array([5.e-324])
Truth: True | Length: 1
Expr: np.zeros((1,)) | Value: array([0.])
Truth: False | Length: 1
Expr: np.zeros((2,)) | Value: array([0., 0.])
Truth: No Truthiness | Length: 2
Expr: np.ones((1,)) | Value: array([1.])
Truth: True | Length: 1
Expr: np.ones((2,)) | Value: array([1., 1.])
Truth: No Truthiness | Length: 2
Expr: pd.Series() | Value: Series([], dtype: float64)
Truth: No Truthiness | Length: 0
Expr: pd.DataFrame() | Value: Empty DataFrame
Truth: No Truthiness | Length: 0
Expr: xr.DataArray() | Value: <xarray.DataArray ()>
Truth: True | Length: No length
Expr: linkedadt.LinkedList() | Value: <linkedadt.LinkedList object at 0x7f08d8d77f40>
Truth: False | Length: 0
--
Keeping medicines from the bloodstreams of the sick; food
from the bellies of the hungry; books from the hands of the
uneducated; technology from the underdeveloped; and putting
advocates of freedom in prisons. Intellectual property is
to the 21st century what the slave trade was to the 16th.
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