python文件编辑

import os


class mpy_edit(object):
    def __init__(self,file_name):
        self.file_name=file_name
        self.read_file(self.file_name)
    def read_file(self,file_name):
        if os.path.exists(file_name):
            self.size=os.path.getsize(file_name)
            self.f=open(file_name,"r")
            self.file_lines=self.f.readlines()
            self.all=len(self.file_lines)
            self.now=0
            self.f.close()
        else:
            return "NO FILE"
    def line_num(self,line_num):
        if self.all>line_num+1:
            self.now=line_num+1
            return self.file_lines[line_num]
        else:
            line_num=self.all-1
            self.now=self.all-1
            return self.file_lines[self.now]
        
    def read(self):
        return self.line_num(self.now)
    def edit_line(self,line_num,str_info):
        self.file_lines[line_num]=str_info
    def save(self,file_name=False):
        if not file_name:
            file_name=self.file_name
        nf=open(file_name,"w")
        for i in self.file_lines:
            nf.write(i)
        nf.close()

    
f=mpy_edit("ttt.txt")



print(f.line_num(14))