Python实现随机游走的示例代码

# Python code for 1-D random walk.
import random
import numpy as np
import matplotlib.pyplot as plt

# Probability to move up or down
prob = [0.05, 0.95]

# statically defining the starting position
start = 2
positions = [start]

# creating the random points
rr = np.random.random(1000)
downp = rr < prob[0]
upp = rr > prob[1]


for idownp, iupp in zip(downp, upp):
	down = idownp and positions[-1] > 1
	up = iupp and positions[-1] < 4
	positions.append(positions[-1] - down + up)

# plotting down the graph of the random walk in 1D
plt.plot(positions)
plt.show()

# Python code for 2D random walk.
import numpy
import pylab
import random

# defining the number of steps
n = 100000

#creating two array for containing x and y coordinate
#of size equals to the number of size and filled up with 0's
x = numpy.zeros(n)
y = numpy.zeros(n)

# filling the coordinates with random variables
for i in range(1, n):
	val = random.randint(1, 4)
	if val == 1:
		x[i] = x[i - 1] + 1
		y[i] = y[i - 1]
	elif val == 2:
		x[i] = x[i - 1] - 1
		y[i] = y[i - 1]
	elif val == 3:
		x[i] = x[i - 1]
		y[i] = y[i - 1] + 1
	else:
		x[i] = x[i - 1]
		y[i] = y[i - 1] - 1
	

# plotting stuff:
pylab.title("Random Walk ($n = " + str(n) + "$ steps)")
pylab.plot(x, y)
pylab.savefig("rand_walk"+str(n)+".png",bbox_inches="tight",dpi=600)
pylab.show()