python 文件插入第一行

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

 fileinput.input的inplace必须要设为1，以便让stdout被重定向到输入文件里：

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

 

评论

2 楼 miniduan 2013-06-21  

i here by provide one that works:

import os

def prepend(filename, data, bufsize=1<<15):
    # backup the file
    backupname = filename + os.extsep+'bak'
    try: os.unlink(backupname) # remove previous backup if it exists
    except OSError: pass
    os.rename(filename, backupname)

    # open input/output files,  note: outputfile's permissions lost
    with open(backupname) as inputfile, open(filename, 'w') as outputfile:
        # prepend
        outputfile.write(data)
        # copy the rest
        buf = inputfile.read(bufsize)
        while buf:
            outputfile.write(buf)
            buf = inputfile.read(bufsize)

    # remove backup on success
    try: os.unlink(backupname)
    except OSError: pass

print 'austin test'
prepend('D:\\aduan\\program\\abc.txt','i love her\n')
print 'austin test done'


output:
D:\aduan\program>type abc.txt
i love youi love you
D:\aduan\program>type abc.txt
i love youi love you
D:\aduan\program>python python.insert1stLine.py
austin test
austin test done

D:\aduan\program>type abc.txt
i love her

1 楼 miniduan 2013-06-21  

验证了一下，不好用啊：

import fileinput, os

def file_insert(fname,linenumbers=[],strings=[]): 
    """
    Insert several strings to lines with linenumbers repectively.

    The elements in linenumbers must be in increasing order and len(strings)
    must be equal to or less than len(linenumbers).

    The extra lines ( if len(linenumbers)> 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(linenumbers) and linenumbers[i]==lineno: 
                if i>=len(strings): 
                    print "\n",line 
                else: 
                    print strings[i] 
                    print line 
                i += 1 
            else: 
                print line

print 'austin test'
file_insert('D:\\aduan\\program\\abc.txt', [1,4,5], ['i love you'])
print 'austin test done'