python基础_文件操作实现全文或单行替换的方法

Python  /  管理员 发布于 7年前   203

python修改文件时，使用w模式会将原本的文件清空/覆盖。可以先用读（r）的方式打开，写到内存中,然后再用写（w）的方式打开。

1、替换文本中的taste 为 tasting

Yesterday when I was young昨日当我年少轻狂The taste of life was sweet生命的滋味是甜的As rain upon my tongue

#将文件读取到内存中with open("./fileread.txt","r",encoding="utf-8") as f: lines = f.readlines() #写的方式打开文件with open("./fileread.txt","w",encoding="utf-8") as f_w: for line in lines:  if "taste" in line:   #替换   line = line.replace("taste","tasting")  f_w.write(line)

2、全文中搜索替换或者单行替换

#文本内容Yesterday when I was young昨日当我年少轻狂The taste of life was sweet生命的滋味是甜的As rain upon my tonguetastetastetastetaste

#定义一个函数，带有4个参数#x 表示要更新的文件名称#y 表示要被替换的内容#z 表示 替换后的内容#s 默认参数为 1 表示只替换第一个匹配到的字符串# 如果参数为 s = 'g' 则表示全文替换def string_switch(x,y,z,s=1): with open(x, "r", encoding="utf-8") as f:  #readlines以列表的形式将文件读出  lines = f.readlines()  with open(x, "w", encoding="utf-8") as f_w:  #定义一个数字，用来记录在读取文件时在列表中的位置  n = 0  #默认选项，只替换第一次匹配到的行中的字符串  if s == 1:   for line in lines:    if y in line:     line = line.replace(y,z)     f_w.write(line)     n += 1     break    f_w.write(line)    n += 1   #将剩余的文本内容继续输出   for i in range(n,len(lines)):    f_w.write(lines[i])  #全局匹配替换  elif s == 'g':   for line in lines:    if y in line:     line = line.replace(y,z)    f_w.write(line)

测试

1)默认参数 1，只替换匹配到的第一行

string_switch("fileread.txt","taste","tasting") #结果Yesterday when I was young昨日当我年少轻狂The tasting of life was sweet生命的滋味是甜的As rain upon my tonguetastetastetastetaste

2)全局替换

string_switch("fileread.txt","taste","tasting","g") #结果Yesterday when I was young昨日当我年少轻狂The tasting of life was sweet生命的滋味是甜的As rain upon my tonguetastingtastingtastingtasting

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