with open('seu_arquivo.txt', 'r', encoding='utf-8') as file:
    new_line=[]
    for line in file:
        new_line.append(line)
        if not # Aqui vai sua condiçao para concatenar com a(s) outra(s) linha(s):
            print(''.join(new_line))
            new_line=[]
    if new_line:
        print(''.join(new_line))