打印空心三角形

for i in range(1,7):
    for j in range(1,7-i):
        print(" ",end="")
    for k in range(1,2*i-1+1):
        if k==1 or k==2*i-1 or i==6:
            print("*",end="")
        else:
            print(" ",end="")
    print()