Python3使用mmap进行文件内容替换

  你想将文件里面的所有'hello'字符串全部换成'nihao',而又不想创建临时文件，可以尝试如下方法：

import mmap
import contextlib


def modify_text_file(file,src,dst):
    if len(src) != len(dst):
        print ("Sorry,替换字符串的长度不一样，无法进行替换!")
        return
    with open("D:\\123.txt",'r+') as fp:
        with contextlib.closing(mmap.mmap(fp.fileno(), 0,access=mmap.ACCESS_WRITE)) as mm:
            mm.seek(0)
            while True:
                local = mm.find(src)
                if local >= 0:
                    print (local)
                    mm[local:local+len(src)] = dst
                else:
                    break
    print ('替换完成!')


if __name__ == '__main__':
    file = 'D:\\123.txt'
    src = b'hello
    dst = b'nihao'

    modify_text_file(file,src,dst)

如果文件不太大，也可以使用正则替换：

import re
import mmap
import contextlib


def modify_text_file(file,src,dst):
    if len(src) != len(dst):
        print ("Sorry,替换字符串的长度不一样，无法进行替换!")
        return
    reg = re.compile(src,re.IGNORECASE)
    with open("D:\\123.txt",'r+') as fp:
        with contextlib.closing(mmap.mmap(fp.fileno(), 0,access=mmap.ACCESS_WRITE)) as mm:
            mm.seek(0)
            data = reg.sub(dst,mm)
            mm.write(data)
    print ('All OVER')
            

if __name__ == '__main__':
    file = 'D:\\123.txt'
    src = b'hello'
    dst = b'nihao'

    modify_text_file(file,src,dst)