def test_cells():
"""
Create a Cells object
"""
from pica.cells import Cells
cells = Cells(3, 2, 'state')
assert_equals(cells.width, 3)
assert_equals(cells.height, 2)
for x in range(3):
for y in range(2):
assert_equals(cells.cell(x, y), 'state')
for x, y in ((-1, -1), (0, 4), (3, 2)):
assert_is_none(cells.cell(x, y))
for y in (-1, 2, 3):
with assert_raises(ValueError):
# because row is a generator, we can't just call cells.row,
# as the ValueError won't be thrown until access.
list(cells.row(y))
for y in range(2):
for cell in cells.row(y):
assert_equals(cell, 'state')
for x, y in ((-1, -1), (0, 4), (3, 2)):
with assert_raises(ValueError):
cells.update(x, y, 'new state')
for y in range(2):
for cell in cells.row(y):
assert_equals(cell, 'state')
for x in range(3):
for y in range(2):
assert_equals(cells.cell(x, y), 'state')
cells.update(x, y, (x, y))
assert_equals(cells.cell(x, y), (x, y))
for y in range(2):
for x, cell in enumerate(cells.row(y)):
assert_equals(cell, (x, y))
class Automata:
"""
A cellular automata.
"""
def __init__(self, width, height, initial_state, *rules):
self._cells = Cells(width, height, initial_state)
self._rules = rules
@property
def cells(self):
return self._cells
def randomize(self, states):
"""
randomize the automata.
states: an iterable of possible states.
"""
if not states:
raise ValueError(states)
for x in range(self._cells.width):
for y in range(self._cells.height):
self._cells.update(x, y, choice(states))
def step(self):
"""
Take a step in the simulation. Returns a set of Changes.
"""
changes = set()
for x in range(self._cells.width):
for y in range(self._cells.height):
possibilities = Counter()
forbidden = set()
for rule in self._rules:
rule.reset()
result = rule(self._cells, x, y)
if result:
if result.difference is None:
forbidden.add(result.state)
else:
possibilities[result.state] += result.difference
for state in forbidden:
del possibilities[state] # works even if state not a key
total = sum(possibilities.values())
if total: # at least one possibility
value = total * random()
tally = 0
for state, probability in possibilities.items():
tally += probability
if value < tally:
if self._cells.cell(x, y) != state: # new state
changes.add(Change(x, y, state))
break
for change in changes:
self._cells.update(change.x, change.y, change.state)
return changes
