Someone

from random import *
poss = [['u','U'],['r','R']]
scramble=''
num=4
axis=2
for t in range(25):
    ax=randint(0,1)
    y=randint(0,1)
    if ax == axis:
        while y==num:
            y=randint(0,1)
            
    num=y
    axis=ax
    scramble=scramble+poss[ax][y]+' '
print scramble