10-1 Python 学习笔记：在文本编辑器中新建一个文件，写几句话来总结一下你至此学到的Python 知识，其中每一行都以“In Python you can”打头。将这个文件命名为learning_python.txt，并将其存储到为完成本章练习而编写的程序所在的目录中。编写一个程序，它读取这个文件，并将你所写的内容打印三次：第一次打印时读取整个文件；第二次打印时遍历文件对象；第三次打印时将各行存储在一个列表中，再在with 代码块外打印它们。

新建文件learning_python.txt并添加如下内容

1 In Python you can Handle file
2 In Python you can Automatic operation and maintenance
3 In Python you can make AI

编写python代码

 1 filename='learning_python.txt'
 2 with open(filename) as file_object:
 3     contents = file_object.read()
 4     print(contents.rstrip())
 5 
 6 print('')
 7 
 8 with open(filename) as file_object:
 9     for line in file_object:
10         print(line.rstrip())
11 
12 print('')
13 
14 with open(filename) as file_object:
15     lines = file_object.readlines()
16for line in lines:
17     print(line.rstrip())

执行结果

 1 In Python you can Handle file
 2 In Python you can Automatic operation and maintenance
 3 In Python you can make AI
 4 
 5 In Python you can Handle file
 6 In Python you can Automatic operation and maintenance
 7 In Python you can make AI
 8 
 9 In Python you can Handle file
10 In Python you can Automatic operation and maintenance
11 In Python you can make AI

总结：

with 在不需要访问文件后将其关闭

open()返回一个表示文件对象，python将这个文件对象储存到 file_object变量里

read()方法读取文件对象的全部内容，并将其作为一个长长的字符串存储在变量contents中

readlines()方法逐行读取文件对象