diy.py

# 写入同学们的捐赠明细：'小兰：12本'、'小丽：11本'、'李文：9本'、'张伟：16本'
# fg=open(r"C:\Users\Administrator\Desktop\book.txt","w",encoding="utf-8")
# fg.write('小兰：12本\n')
# fg.write('小丽：11本\n')
# fg.write('李文：9本\n')
# fg.write('张伟：16本')
# fg.close()
# with open(r"C:\Users\Administrator\Desktop\book.txt","a",encoding="utf-8")as fg:
#     fg.write("小强:12\n")   
#     fg.write("李明:15\n")
new_fg=""
with open(r"C:\Users\Administrator\Desktop\book.txt","r",encoding="utf-8")as fg:
    for i in fg:
        if "小兰：12本" in i:
            i=i.replace("12","14")
            
        if "小强:12" in i:
            i=i.replace("12","11")
        new_fg=new_fg+i
with open(r"C:\Users\Administrator\Desktop\book.txt","w",encoding="utf-8")as fg:
    fg.write(new_fg)