python打印字母菱形

a = "ABCDEFGHIJKLMNOPQRSTUVWXY" 
rows = int(input("请输入行数"))
c = rows//2+1

if rows>3 and rows%3!=0:
    for i in range(c+1):
        b = ""
        for j in range(0,i):
            b += a[j]
        for j in range(i-2,-1,-1):
            b += a[j]
        for j in range(c-i):
            print(" ",end='')
        print(b)

    for i in range(rows-c,-1,-1):
        b = ""
        for j in range(0,i):
            b += a[j]
        for j in range(i-2,-1,-1):
            b += a[j]
        for j in range(rows-c-i+1):
            print(" ",end='')
        print(b)
else:
    print("请输入一个大于3且除以3不等于0的数")