转 python trace walk DEMO

#quote from ‘introduction to computation and programming 
#using Python, revised, MIT press‘
import random
import pylab
 
def stdDev(X):
    mean = sum(X)/len(X)
    tot = 0.0
    for x in X:
        tot += (x-mean)**2
    return (tot/len(X))**0.5
    
    
def CV(X):
    mean = sum(X)/len(X)
    return stdDev(X)/mean
    
class Location(object):
    
    def __init__(self, x, y):
        """x and y are floats"""
        self.x = x
        self.y = y
    
    def move(self, deltaX, deltaY):
        """deltaX and deltaY are floats"""
        return Location(self.x + deltaX, self.y + deltaY)
        
    def getX(self):
        return self.x
        
    def getY(self):
        return self.y
        
    def distFrom(self, other):
        ox = other.x
        oy = other.y
        xDist = self.x - ox
        yDist = self.y - oy
        return (xDist**2 + yDist**2)**0.5
    
    def __str__(self):
        return ‘<‘ + str(self.x) + ‘, ‘ + str(self.y) + ‘>‘
        
class Field(object):
    
    def __init__(self):
        self.drunks = {}
        
    def addDrunk(self, drunk, loc):
        if drunk in self.drunks:
            raise ValueError(‘Duplicate drunk‘)
        else:
            self.drunks[drunk] = loc
            
    def moveDrunk(self, drunk):
        if drunk not in self.drunks:
            raise ValueError(‘Drunk not in field‘)
        xDist, yDist = drunk.takeStep()
        currentLocation = self.drunks[drunk]
        #use move method of Location to get new location
        self.drunks[drunk] = currentLocation.move(xDist, yDist)
        
    def getLoc(self, drunk):
        if drunk not in self.drunks:
            raise ValueError(‘Drunk not in field‘)
        return self.drunks[drunk]
        
class Drunk(object):
    
    def __init__(self, name = None):
        """Assumes name is a str"""
        self.name = name
        
    def __str__(self):
        if self != None:
            return self.name
        return ‘Anonymous‘
        
class UsualDrunk(Drunk):
    def takeStep(self):
        stepChoices = [(0.0, 1.0), (0.0, -1.0), (1.0, 0.0), (-1.0, 0.0)]
        return random.choice(stepChoices)
 
class ColdDrunk(Drunk):
    def takeStep(self):
        stepChoices = [(0.0, 1.0), (0.0, -2.0), (1.0, 0.0), (-1.0, 0.0)]
        return random.choice(stepChoices)
        
class EWDrunk(Drunk):
    def takeStep(self):
        stepChoices = [(1.0, 0.0), (-1.0, 0.0)]
        return random.choice(stepChoices)
        
class styleIterator(object):
    def __init__(self, styles):
        self.index = 0
        self.styles = styles
        
    def nextStyle(self):
        result = self.styles[self.index]
        if self.index == len(self.styles) - 1:
            self.index = 0
        else:
            self.index += 1
        return result
 
def traceWalk(drunkKinds, numSteps):
    styleChoices = styleIterator((‘b+‘, ‘r^‘, ‘mo‘))
    f = Field()
    for dClass in drunkKinds:
        d = dClass()
        f.addDrunk(d, Location(0, 0))
        locs = []
        for s in range(numSteps):
            f.moveDrunk(d)
            locs.append(f.getLoc(d))
        xVals = []
        yVals = []
        for l in locs:
            xVals.append(l.getX())
            yVals.append(l.getY())
        curStyle = styleChoices.nextStyle()
        pylab.plot(xVals, yVals, curStyle,
                   label = dClass.__name__)
    pylab.title(‘Spots Visited on Walk (‘
                 + str(numSteps) + ‘ steps)‘)
    pylab.xlabel(‘Steps East/West of Origin‘)
    pylab.ylabel(‘Steps North/South of Origin‘)
    pylab.legend(loc = ‘best‘)
 
traceWalk((UsualDrunk, ColdDrunk, EWDrunk), 200)
pylab.show()