new_a=""
with open(r'C:\Users\md100\Desktop\liu.txt','r',encoding='utf-8') as fel:
    # print(a)
    for i in fel:
        print(i)
        if '小兰: 12本'in i:
            i=i.replace('小兰: 12本','小兰: 14本')
        
        new_a+=i
print(new_a)
with open(r'C:\Users\md100\Desktop\liu.txt','w',encoding='utf-8') as fel:
    fel.write(new_a)