正在学习Python，但是在Learn Python The Hard Way Exercise 20中，按照作者给出的代码，我在Powershell上运行，得到的输出结果是这样的：

First let's print the whole file: a aaaaaaaa aaaaaaaaaaaa aaaaaaaaaaaa Now let's rewind, kind of like a tape. Let's print three lines: a aaaaaaaa aaaaaaaaaaaa aaaaaaaaaaaa

可是本来应该是这样的：

$ python ex20.py test.txt First let's print the whole file: This is line 1 This is line 2 This is line 3 Now let's rewind, kind of like a tape. Let's print three lines: 1 This is line 1 2 This is line 2 3 This is line 3

哪里出问题了？