《python核心编程》笔记

创建文件（makeTextFile.py）脚本提醒用户输入一个尚不存在的文件名，然后由用户输入文件每一行，最后将所有文本写入文本文件

 1 #!/usr/bin/env python
 2 
 3 'makeTextFile.py -- creat text file'
 4 
 5 import os
 6 ls = os.linesep
 7 
 8 # get file name
 9 while True:
10 if os.path.exists(fname):          #不存在返False，存在返True
11      print "ERROR: '%s' already exists" % fname
12 else: 
13       break
14 
15 #get file content (text) lines
16 all = []
17 print "
Enter lines ('.' by itself to quit).
"
18 
19 #loop until user terminates input 
20 while True:
21      entry = raw_input('>')
22      if entry == '.':
23           break
24      else:
25           all.append(entry)
26 
27 #write lines to file with proper line-ending
28 fobj = open(fname, 'w')
29 fobj.writelines(['%s%s' % (x,ls) for x in all])
30 #列表解析，将列表中每行（每个元素）都写入文件，两个%s分别是字符串和每行结束符
31 fobj.close
32 print 'DONE!'

文件读取和显示(readTextFile.py)

 1 #!/user/bin/env python
 2 
 3 'readTextFile.py -- read and display text file'
 4 
 5 # get filename
 6 fname = raw_input('Enter filename')
 7 print          #隔开提示和文本
 8 # attempt to open file for reading
 9 try:
10      fobj = open(fname, 'r')
11 except IOError, e:
12      print "*** file open error:",e
13 else:
14      # dispaly content to the screen
15      for eachLine in fobj
16           print eachLine,
17      fobj.close()