python2.7实现杨辉三角

n=10an=[1]*n# print anfor i in range(n):    for j in range(i-1,0,-1):        print j,        an[j]=an[j]+an[j-1]    # print an[0:i+1]        print an[j],    print "\t".join(map(lambda x:str(x),an[0:i+1]))