运用Python中的内置函数open()与文件进行交互
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
>>> 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：
>>> 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：
>>> data.seek(0) #使用seek()方法回到文件起始位置 0 >>> 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()