Python3使用mmap进行文件内容替换

短命女 2022-03-10 08:22 209阅读 0赞

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)

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