auto save

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'
+# file = open(r'C:\Users\Administrator\Desktop\book.txt','w',encoding='utf-8')
+# file.write('小兰：12本\n小丽：11本\n李文：9本\n张伟：16本\n')
+# file.close()
+
+# with open(r'C:\Users\Administrator\Desktop\book.txt','a',encoding='utf-8') as file:
+#     file.write('小强：12本\n李明：15本\n')
+
+new_str=''   # 定义变量保存更新之后的内容
+with open(r'C:\Users\Administrator\Desktop\book.txt','r',encoding='utf-8') as file:
+    for i in file:
+        #print(i)
+        if '小强：12本' in i:
+            i = i.replace('小强：12本','小强：13本')
+        new_str += i
+#print(new_str)
+# 把更新后的内容一次写入到原文件中
+with open(r'C:\Users\Administrator\Desktop\book.txt','w',encoding='utf-8') as file:
+    file.write(new_str)
+# 查看更新后的文件内容
+with open(r'C:\Users\Administrator\Desktop\book.txt','r',encoding='utf-8') as file:
+    for i in file:
+        print(i)
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