python基础--文件操作实现全文或单行替换

时间：2021-10-31 17:00:06

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 tongue

taste

taste

taste

taste

#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 tongue

taste

taste

taste

taste

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 tongue

tasting

tasting

tasting

tasting

　　

　

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