先放一段py
import pylab as pl
a = []
b = []
step = 0.005
x = 0
n = 1 / step
y = 1
for i in range(int(n)+1):
a.append(x)
b.append(y)
y = y + step*(y**2 + x**2)
x += step
pl.plot(a,b,'o')
pl.title('step = 0.1')
pl.xlabel('x axis')
pl.ylabel('y axis')
pl.show()