python修改文件時，使用w模式會將原本的文件清空/覆蓋?？梢韵扔米x(r)的方式打開，寫到內存中,然后再用寫(w)的方式打開。替換文本中的taste 為 tastingYesterday when I was young

昨日當我年少輕狂

The taste of life was sweet

生命的滋味是甜的

As rain upon my tongue#將文件讀取到內存中

with open("./fileread.txt","r",encoding="utf-8") as f:

lines = f.readlines()

#寫的方式打開文件

with open("./fileread.txt","w",encoding="utf-8") as f_w:

for line in lines:

if "taste" in line:

#替換

line = line.replace("taste","tasting")

f_w.write(line)

2.全文中搜索替換或者單行替換#文本內容

Yesterday when I was young

昨日當我年少輕狂

The taste of life was sweet

生命的滋味是甜的

As rain upon my tongue

taste

taste

taste

taste#定義一個函數，帶有4個參數

#x 表示要更新的文件名稱

#y 表示要被替換的內容

#z 表示 替換后的內容

#s 默認參數為 1 表示只替換第一個匹配到的字符串

# 如果參數為 s = 'g' 則表示全文替換

def string_switch(x,y,z,s=1):

with open(x, "r", encoding="utf-8") as f:

#readlines以列表的形式將文件讀出

lines = f.readlines()

with open(x, "w", encoding="utf-8") as f_w:

#定義一個數字，用來記錄在讀取文件時在列表中的位置

n = 0

#默認選項，只替換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

#將剩余的文本內容繼續輸出

for i in range(n,len(lines)):

f_w.write(lines[i])

#全局匹配替換

elif s == 'g':

for line in lines:

if y in line:

line = line.replace(y,z)

f_w.write(line)

測試

1)默認參數 1，只替換匹配到的第一行string_switch("fileread.txt","taste","tasting")

#結果

Yesterday when I was young

昨日當我年少輕狂

The tasting of life was sweet

生命的滋味是甜的

As rain upon my tongue

taste

taste

taste

taste

2)全局替換string_switch("fileread.txt","taste","tasting","g")

#結果

Yesterday when I was young

昨日當我年少輕狂

The tasting of life was sweet

生命的滋味是甜的

As rain upon my tongue

tasting

tasting

tasting

tasting

總結

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