diy.py

new_data=''
with open(r'c:\Users\CM\Desktop\text.txt','r',encoding='utf-8')as flle1:
    for data in flle1:
        if'小强:10本'in data:
            data=str.repalace('小强：10本','小强:11本')

with open(r'c:\Users\CM\Desktop\text.txt','w',encoding='utf-8')as flle1:      
    flle1.new_data