def _sieve():
yield 1
candidates = Stream(count(2))
while True:
prime, rest = candidates.advance()
yield prime
candidates = candidates.filter(_make_filter(prime))
def test_max():
def first(seq):
return seq[0]
def second(seq):
return seq[1]
assert Stream([2, 1, 5, 4, -6]).max() == 5
s = Stream([('a', 2), ('z', 1), ('c', 7)])
assert s.max(key=first) == ('z', 1)
assert s.max(key=second) == ('c', 7)
def caesar_cypher(message: str, shift: int) -> str:
num_letters = (ord('z') - ord('a')) + 1
ascii_cycle = partials.compose3(
partials.add(-ord('a')),
partials.modulo(num_letters),
partials.add(ord('a')))
return ''.join(Stream(message).map(ord).map(partials.add(shift)).map(ascii_cycle).map(chr))
def test_for_each():
def _side_effect(inc: int):
global accum
accum += inc
Stream(count(1)).take(5).for_each(_side_effect)
assert accum == 15
def caesar_cypher_with_special_chars(message: str, shift: int) -> str:
a = ord('a')
z = ord('z')
num_letters = (z - a) + 1
ascii_cycle = partials.compose3(
partials.add(-a),
partials.modulo(num_letters),
partials.add(a))
return ''.join(Stream(message).map(ord).map_if(
condition=partials.is_in(range(a, z + 1)),
func=partials.add(shift)
).map_if(
condition=partials.is_in(range(a + shift, z + shift + 1)),
func=ascii_cycle
).map(chr))
def sieve_eratosthenes() -> Stream[int]:
def _make_filter(
prime: int
): # HACK: Necessary because python closures are late-binding
return lambda x: x % prime != 0
def _sieve():
yield 1
candidates = Stream(count(2))
while True:
prime, rest = candidates.advance()
yield prime
candidates = candidates.filter(_make_filter(prime))
return Stream(_sieve())
def sieve_eratosthenes_pyfunctional() -> Stream[int]:
def _make_filter(
prime: int
): # HACK: Necessary because python closures are late-binding
return lambda x: x % prime != 0
def _sieve():
yield 1
candidates = seq(count(2))
while True:
prime = candidates.first()
candidates.drop(1)
yield prime
candidates = candidates.filter(_make_filter(prime))
return Stream(_sieve())
def test_map():
assert Stream([1, 5, 3]).map(lambda x: x * 2).to_list() == [2, 10, 6]
def test_filter_when_items_are_tuples():
assert (Stream([('a', 1), ('b', 5), ('c', 3)
]).filter(lambda k, v: v > 3).to_list()) == [('b', 5)]
def test_map_when_items_are_tuples():
assert (Stream([('a', 1), ('b', 5), ('c', 3)
]).map(lambda k, v: (k, v * 2)).to_list()) == [('a', 2),
('b', 10),
('c', 6)]
def test_extend():
assert Stream([1, 2]).extend(3).to_list() == [1, 2, 3]
def test_append():
assert Stream([1, 2, 3]).append(0).to_list() == [0, 1, 2, 3]
def test_take():
assert Stream(count(1, 2)).take(3).to_list() == [1, 3, 5]
def test_to_list():
s = Stream(['a', 'b', 'c'])
assert s.to_list() == ['a', 'b', 'c']
assert s.to_list() == ['a', 'b', 'c']
def test_zip():
ascii_a_to_c = range(ord('a'), ord('d'))
assert Stream(cycle(ascii_a_to_c)).map(chr).zip(
count(1)).take(5).to_list() == [('a', 1), ('b', 2), ('c', 3), ('a', 4),
('b', 5)]
def test_iter():
s = Stream([0, 1, 2, 3])
for i, x in zip(range(4), s):
assert i == x
def test_filter():
assert Stream(count(1)).filter(lambda x: x % 7 == 0).take(4).to_list() == [
7, 14, 21, 28
]
def test_drop():
assert Stream(count(1, 2)).drop(3).first() == 7
def test_chain():
assert Stream([1, 2, 3]).chain(Stream(
['a', 'b',
'c']), count(4)).take(8).to_list() == [1, 2, 3, 'a', 'b', 'c', 4, 5]
def caesar_cypher2(message: str, shift: int) -> str:
alphabet = 'abcdefghijklmnopqrstuvwxyz'
return Stream(message).map_if(
condition=_.is_in(alphabet),
func=compose4(alphabet.find, _.add(shift), _.modulo(len(alphabet)), alphabet.__getitem__)
).join()
def test_first():
assert Stream([2, 1, 4]).first() == 2
def test_advance():
x, rest = Stream(count(3)).take(4).advance()
assert x == 3
assert rest.to_list() == [4, 5, 6]
def test_reduce():
assert Stream([1, 2, 3, 4]).reduce(lambda k, v: k + v) == 10