python-修改文件內容並保存的3種方法

轉載：http://www.cnblogs.com/wc-chan/p/8085452.html

一、修改原文件方式

def alter(file,old_str,new_str):
    """
    替換文件中的字符串
    :param file:文件名
    :param old_str:就字符串
    :param new_str:新字符串
    :return:
    
    """
    file_data = ""
    with open(file, "r", encoding="utf-8") as f:
        for line in f:
            if old_str in line:
                line = line.replace(old_str,new_str)
            file_data += line
    with open(file,"w",encoding="utf-8") as f:
        f.write(file_data)

alter("file1", "09876", "python")

二、把原文件內容和要修改的內容寫到新文件中進行存儲的方式

import os
def alter(file,old_str,new_str):
    """
    將替換的字符串寫到一個新的文件中，然後將原文件刪除，新文件改爲原來文件的名字
    :param file: 文件路徑
    :param old_str: 需要替換的字符串
    :param new_str: 替換的字符串
    :return: None
    """
    with open(file, "r", encoding="utf-8") as f1,open("%s.bak" % file, "w", encoding="utf-8") as f2:
        for line in f1:
            if old_str in line:
                line = line.replace(old_str, new_str)
            f2.write(line)
    os.remove(file)
    os.rename("%s.bak" % file, file)

alter("file1", "python", "測試")

三、python使用正則表達式 替換文件內容re.sub方法替換

import re,os
def alter(file,old_str,new_str):

    with open(file, "r", encoding="utf-8") as f1,open("%s.bak" % file, "w", encoding="utf-8") as f2:
        for line in f1:
            f2.write(re.sub(old_str,new_str,line))
    os.remove(file)
    os.rename("%s.bak" % file, file)
alter("file1", "admin", "password")