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| import mathimport randomimport pylab
class Location(object):
def __init__(self, x, y):
self.x = float(x)
self.y = float(y)
def move(self, xc, yc):
return Location(self.x + float(xc), self.y+float(yc))
def getCoords(self):
return self.x, self.y
def getDist(self, other):
ox, oy = other.getCoords()
xDist = self.x - ox
yDist = self.y - oy
return math.sqrt(xDist**2 + yDist ** 2)
class CompassPt(object):
possibles = ('N', 'S', 'E', 'W')
def __init__(self, pt):
if pt in self.possibles:
self.pt = pt
else:
raise ValueError('in CompassPt.__init__')
def move(self, dist):
if self.pt == 'N':
return (0, dist)
elif self.pt == 'S':
return (0, -dist)
elif self.pt == 'E':
return (dist, 0)
elif self.pt == 'W':
return (-dist, 0)
else:
raise ValueError('in compassPt.move')
class Field(object):
def __init__(self, drunk, loc):
self.drunk = drunk
self.loc = loc
def move(self, cp, dist):
oldLoc = self.loc
xc, yc = cp.move(dist)
self.loc = oldLoc.move(xc, yc)
def getLoc(self):
return self.loc
def getDrunk(self):
return self.drunk
class Drunk(object):
def __init__(self, name):
self.name = name
def move(self, field, time=1):
if field.getDrunk() != self:
raise ValueError('Drunk.move called with drunk not in field')
for i in range(time):
pt = CompassPt(random.choice(CompassPt.possibles))
field.move(pt, 1)
def performTrial(time, f):
start = f.getLoc()
distances = [0.0]
for t in range(1, time+1):
f.getDrunk().move(f)
newLoc = f.getLoc()
distance = newLoc.getDist(start)
distances.append(distance)
return distances
drunk = Drunk('a man')
for i in range(3):
f = Field(drunk, Location(0, 0))
distances = performTrial(500, f)
pylab.plot(distances)
pylab.title('random walk')
pylab.xlabel('time')
pylab.ylabel('distance from origin')
pylab.show()
assert False
|