从零学python系列之从文件读取和保存数据

在HeadFirstPython网站中下载所有文件，解压后以chapter 3中的"sketch.txt"为例：

新建IDLE会话，首先导入os模块，并将工作目录却换到包含文件"sketch.txt"的文件夹，如C:\\Python33\\HeadFirstPython\\chapter3

复制代码 代码如下:

import os
os.getcwd() #查看当前工作目录
'C:\\Python33'
os.chdir('C:/Python33/HeadFirstPython/chapter3') #切换包含数据文件的文件夹
os.getcwd() #查看切换后的工作目录
'C:\\Python33\\HeadFirstPython\\chapter3'

打开文件"sketch.txt"，读取并显示前两行：

复制代码 代码如下:

data=open('sketch.txt')
print(data.readline(),end='')
Man: Is this the right room for an argument?
print(data.readline(),end='')
Other Man: I've told you once.

回到文件起始位置，使用for语句处理文件中的每行，最后关闭文件：

复制代码 代码如下:

data.seek(0) #使用seek()方法回到文件起始位置
for each_line in data:
print(each_line,end='')

Man: Is this the right room for an argument?
Other Man: I've told you once.
Man: No you haven't!
Other Man: Yes I have.
Man: When?
Other Man: Just now.
Man: No you didn't!
Other Man: Yes I did!
Man: You didn't!
Other Man: I'm telling you, I did!
Man: You did not!
Other Man: Oh I'm sorry, is this a five minute argument, or the full half hour?
Man: Ah! (taking out his wallet and paying) Just the five minutes.
Other Man: Just the five minutes. Thank you.
Other Man: Anyway, I did.
Man: You most certainly did not!
Other Man: Now let's get one thing quite clear: I most definitely told you!
Man: Oh no you didn't!
Other Man: Oh yes I did!
Man: Oh no you didn't!
Other Man: Oh yes I did!
Man: Oh look, this isn't an argument!
(pause)
Other Man: Yes it is!
Man: No it isn't!
(pause)
Man: It's just contradiction!
Other Man: No it isn't!
Man: It IS!
Other Man: It is NOT!
Man: You just contradicted me!
Other Man: No I didn't!
Man: You DID!
Other Man: No no no!
Man: You did just then!
Other Man: Nonsense!
Man: (exasperated) Oh, this is futile!!
(pause)
Other Man: No it isn't!
Man: Yes it is!

data.close()