auto save

diy.py

+new_data=""
+with open(r'C:\Users\CM\Desktop\book.txt','r',encoding='utf-8') as file1:
+    for data in file1:
+        if '小强：10本' in data:
+            data = data.replace("小强：10本","小强：12本")
+        new_data += data
+
+with open(r'C:\Users\CM\Desktop\book.txt','w',encoding='utf-8') as file1:
+    file1.write(new_data)
+