Python for loop only saves the last loop in my 2-d array -

i producing 1 dimensional random walks , want loop save maximum distance origin has been reached far, time progresses. 5 random walks produced. code:

for j in range(5):     r = rand(10000)     t = range(10000)     x = zeros(10000)     y = zeros((10000, 5))     in range(10000):         walk = r[i]         if walk < 0.5:             x[i] = x[i-1] - 1             y[:,j]= maximum.accumulate(abs(x))         else:             x[i] = x[i-1] + 1             y[:,j]= maximum.accumulate(abs(x))     plot(t,x, label="walk %d" %(j+1))  title("1-d random walk (position versus time)") xlabel("time") ylabel("position") legend(loc="best") grid() 

the problem after loop iterates on set range (5) output 2-d array includes last iteration. somehow, overwhites previous ones, 10000x5 array last row filled in.

how can make work?

you've, reason, chosen execute

y = zeros((10000, 5)) 

over , on again, each time through outer loop.

as obvious consequence, last assignment y can possibly "take", evidently overriding previous assignment same name. other behavior possibly expect such repeated assignments?!

move assignment outside outer loop, , there no "overriding" of name y.