maximum previous in numpy

Question

Possible Duplicate:
Running maximum of numpy array values

I'm looking for a maximum function in numpy that do something like :

a  = array([0.2,0.3,0.25,0.5,0.2,0.8])
maxi(a)
---> [0.2,0.3,0.3,0.5,0.5,0.8]

thanks