python文件特定行插入和替换实例详解_Python

python提供了read,write,但和很多语言类似似乎没有提供insert。当然真要提供的话，肯定是可以实现的，但可能引入insert会带来很多其他问题，比如在插入过程中crash掉可能会导致后面的内容没来得及写回。

不过用fileinput可以简单实现在特定行插入的需求：

Python代码

									import os 

									import fileinput 

									def file_insert(fname,linenos=[],strings=[]): 

									  """ 

									  Insert several strings to lines with linenos repectively. 

									  The elements in linenos must be in increasing order and len(strings) 

									  must be equal to or less than len(linenos). 

									  The extra lines ( if len(linenos)> len(strings)) will be inserted 

									  with blank line. 

									  """

									  if os.path.exists(fname): 

									    lineno = 0

									    i = 0

									    for line in fileinput.input(fname,inplace=1): 

									      # inplace must be set to 1 

									      # it will redirect stdout to the input file 

									      lineno += 1

									      line = line.strip() 

									      if i<len(linenos) and linenos[i]==lineno: 

									        if i>=len(strings): 

									          print "\n",line 

									        else: 

									          print strings[i] 

									          print line 

									        i += 1

									      else: 

									        print line 

									file_insert('a.txt',[1,4,5],['insert1','insert4'])