每日一题--Python打印金字塔

def day1(num):
    s = 'abcdefghijklmnopqrstuvwxyz' * (num // 26 + 1)
    for i in range(1, num + 1):
        print('{0:^{1}}'.format(s[:i] + s[:i -1][::-1], num * 2 -1))

day1(28)