hacker rank python problem(Alphabet rangoli)

ALPHABET RANGOLI

def print_rangoli(size):
   # your code goes here
    alpha = ['a']
    for i in range(size-1):
        alpha.append(chr(ord(alpha[i]) + 1))

    poped = []
    beta = list(alpha)
    beta.reverse()
    beta.pop() # remove the extra a => e,c,d,b
   
    full_list = list(beta)
    full_list.extend(alpha)
    # to determine the width of the line with no outer dashes
    max_len = len('-'.join(full_list))

    for j in range(1,size+1):
        m_str = ""
        if (j-1) > 0:
            m_str = '-'.join(beta[:j-1]) + '-'
        m_str += '-'.join(alpha[j*-1:])
        string = '{s:{c}^{n}}'.format(s=m_str, n=max_len, c='-')
        poped.append(string)

    # upper part
    print('\n'.join(poped))
    poped.pop()
    poped.reverse()
    # lower part
    print('\n'.join(poped))