def _fetch_next(itr: Iterable[X], n: int) -> Iterable[Tuple[X, ...]]:
"""
Creates generator. Each element is tuple of size "n".
While iterating, first element will be first "n" elements of
Stream, next element will be old "n-1" elements appended with
next element of Stream and so on.
Note that if in first call to this generator, stream has less
than "n" element then ValueError will be thrown.
:param itr:
:param n: a natural number
:return:
"""
if n < 1:
raise ValueError("'n' must be natural number")
chunk = get_chunk(itr, n)
if len(chunk) != n:
# first chunk size must be "n".
raise ValueError("Stream has less than '{}' elements ".format(n))
yield chunk
for e in itr:
chunk = chunk[1:] + (e,)
yield chunk
def test_1(self):
rnd = random()
a, b, size = 0, 10, 10
chunk_size = 3
data = rnd.int_range(a, b, size=size)
itr = iter(data.copy())
for i in range(a, b, chunk_size):
chunk = get_chunk(itr, chunk_size, list)
self.assertListEqual(chunk, data[i:i + chunk_size])
def test_8(self):
data = range(10)
get_chunk(data, range(5, 3)) # should throw exception
def test_5(self):
data = range(10)
get_chunk(data, 0) # should throw exception
def test_4(self):
data = range(10)
get_chunk(data, None) # should throw exception
def test_2(self):
data = ()
self.assertEqual(get_chunk(data, 3), ())
