Added new 'Len' and 'double_chain' functions to utils.

Author: domdfcoding

domdf_python_tools/utils.py

@@ -245,9 +245,11 @@ def strtobool(val: Union[str, bool]) -> bool:
 
 	If val is an integer then its boolean representation is returned. If val is a boolean it is returned as-is.
 
-	True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
-	are 'n', 'no', 'f', 'false', 'off', and '0'.  Raises ValueError if
-	'val' is anything else.
+	:py:obj:`True` values are ``'y'``, ``'yes'``, ``'t'``, ``'true'``, ``'on'``, ``'1'``, and ``1``.
+
+	:py:obj:`False` values are ``'n'``, ``'no'``, ``'f'``, ``'false'``, ``'off'``, ``'0'``, and ``0``.
+
+	:raises: :py:exc:`ValueError` if 'val' is anything else.
 
 	Based on distutils
 	"""
@@ -281,3 +283,52 @@ def enquote_value(value: Any) -> Union[str, bool, float]:
 		return repr(value)
 	else:
 		return f"'{value}'"
+
+
+def Len(obj: Any, start: int = 0, step: int = 1) -> range:
+	"""
+	Shorthand for ``range(len(obj))``.
+
+	Returns an object that produces a sequence of integers from start (inclusive)
+	to len(obj) (exclusive) by step.
+
+	:param obj: The object to iterate over the length of.
+	:param start: The start value of the range.
+	:param step: The step of the range.
+
+	.. versionadded:: 0.4.7
+	"""
+
+	return range(start, len(obj), step)
+
+
+def double_chain(iterable: Iterable[Iterable]):
+	"""
+	Flatten a list of lists of lists into a single list.
+
+	Literally just:
+
+	.. code-block:: python
+
+		chain.from_iterable(chain.from_iterable(iterable))
+
+	Converts
+
+	.. code-block:: python
+
+		[[(1, 2), (3, 4)], [(5, 6), (7, 8)]]
+
+	to
+
+	.. code-block:: python
+
+		[1, 2, 3, 4, 5, 6, 7, 8]
+
+
+	:param iterable: The iterable to
+	:return:
+
+	.. versionadded:: 0.4.7
+	"""
+
+	yield from itertools.chain.from_iterable(itertools.chain.from_iterable(iterable))

tests/test_utils.py

@@ -19,7 +19,7 @@
 
 # this package
 from domdf_python_tools import utils
-from domdf_python_tools.utils import chunks, list2str, list2string, pyversion, str2tuple, tuple2str
+from domdf_python_tools.utils import Len, chunks, double_chain, list2str, list2string, pyversion, str2tuple
 
 
 def test_pyversion():
@@ -389,3 +389,31 @@ def test_cmp():
 
 	assert isinstance(utils.cmp(20, 20), int)
 	assert utils.cmp(20, 20) == 0
+
+
+@pytest.mark.parametrize(
+		"value, expects",
+		[
+				([[(1, 2), (3, 4)], [(5, 6), (7, 8)]], [1, 2, 3, 4, 5, 6, 7, 8]),
+				([[(1, 2), (3, 4)], ((5, 6), (7, 8))], [1, 2, 3, 4, 5, 6, 7, 8]),
+				([((1, 2), (3, 4)), [(5, 6), (7, 8)]], [1, 2, 3, 4, 5, 6, 7, 8]),
+				([((1, 2), (3, 4)), ((5, 6), (7, 8))], [1, 2, 3, 4, 5, 6, 7, 8]),
+				((((1, 2), (3, 4)), ((5, 6), (7, 8))), [1, 2, 3, 4, 5, 6, 7, 8]),
+				((("12", "34"), ("56", "78")), ["1", "2", "3", "4", "5", "6", "7", "8"]),
+				]
+		)
+def test_double_chain(value, expects):
+	assert list(double_chain(value)) == expects
+
+
+def test_len(capsys):
+	assert list(Len("Hello")) == [0, 1, 2, 3, 4]
+	assert list(Len("Hello World")) == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+
+	for val in Len("Hello World"):
+		print(val)
+
+	captured = capsys.readouterr()
+	assert captured.out.splitlines() == ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10"]
+
+	assert Len("Hello") == range(5)