将刚刚创建好的文件打开并读取内容：1一次读取全部内容2每次读取一行

(1) 一次读取全部内容：

with open('test.txt', 'r') as file:
    content = file.read()
    print(content)

输出结果：

Hello, world!
This is a test file.
Hope it works well.

(2) 每次读取一行：

with open('test.txt', 'r') as file:
    for line in file:
        print(line.strip())

输出结果：

Hello, world!
This is a test file.
Hope it works well.