P17 更多文件操作

exists。这个命令将文件名字符串作为参数，如果文件存在的话，它将返回 True，否则将返回 False

 1 from sys import argv
 2 from os.path import exists
 3 
 4 script, from_file, to_file = argv
 5 
 6 print "Copying from %s to %s" % (from_file, to_file)
 7 
 8 # we could do these two on one line too, how?
 9 in_file = open(from_file)
10 indata = in_file.read()
11 
12 print "The input file is %d bytes long" % len(indata)
13 
14 print "Does the output file exist? %r" % exists(to_file)
15 print "Ready, hit RETURN to continue, CTRL-C to abort."
16 raw_input()
17 
18 out_file = open(to_file, 'w')
19 out_file.write(indata)
20 
21 print "Alright, all done."
22 
23 out_file.close()
24 in_file.close()
25

看看你能把这个脚本改多短，我可以把它写成一行