3-1 实现简单的shell sed替换功能

2022-09-28 07:37:21

1.需求

程序1: 实现简单的shell sed替换功能

　　file1 的内容copy到file2

　　输入参数./sed.py $1 $2

　　　　$1替换成$2 （把a替换成% ）

2.个人思路

open file 1 2

file1 内容 copy 到 file2

read 每一行 ，

        if a in line：   

            a替换%        

关闭file1 file2

代码

f1 = open('yes.txt','r+',encoding='utf-8')

f_new = open('yes2.txt','w',encoding='utf-8')

for line in f1.readlines():

    line = line.replace('a','%').strip()

    print(line)

    f_new.writelines(line)

f1.close()

f_new.close()

3.个人心得

3.1 读取文件

　　方法1：记得f1.close() f_new.close()

f1 = open('yes.txt','r+',encoding='utf-8')

f_new = open('yes2.txt','w',encoding='utf-8')

　　方法2：自动帮你关闭文件

with open('yes.txt','r+',encoding='utf-8') as f1:

    with open('yes2.txt','w',encoding='utf-8') as f_new:

            for line in f1.readlines():

3.2 copy全部

方法1：f1 的内容copy到f_new

#全文复制

f1 = open('yes.txt','r+',encoding='utf-8')
f2 = open('yes2.txt','w',encoding='utf-8')

for line in f1.readlines(): 
　　print(line.strip()) 
　　f_new.writelines(line)

#此时光标已经到末尾了

方法2：shutil模块（文本处理，压缩）

import shutil

shutil.copyfile("yes.txt","yes2.txt")

3.3 文件替换

读取 f1 的每行，a替换成%，并且写入到f_new　　

f1 = open('yes.txt','r+',encoding='utf-8')

f2 = open('yes2.txt','w',encoding='utf-8')

for line in f1.readlines():

    line = line.replace('a','%').strip()

    print(line)

    f_new.writelines(line)

3.4 光标问题

注意：全文复制，（读取每一行，然后copy到 f2 ），此时光标已经到文件末尾！执行替换时，已经读取不到内容

错误代码

# coding=utf-8

#打开文件

f1 = open('yes.txt','r+',encoding='utf-8')

f_new = open('yes2.txt','w',encoding='utf-8')

#全文复制

for line in f1.readlines():

    print(line.strip())

    f_new.writelines(line)

#光标已经到末尾了

a = f1.readlines() # a[]

#替换

for line in f1.readlines():

    line = line.replace("a",'%')

    print(line.strip())

    f_new.writelines(line)

3.5 sys模块传入参数

传入参数 sys.argv[1]

import sys

#打开文件

with open('yes.txt','r+',encoding='utf-8') as f1:

    with open('yes2.txt','w',encoding='utf-8') as f_new:

        find_str = sys.argv[1]

        replace_str = sys.argv[2]

cmd 执行代码时，可以带参数　

D:\PycharmProjects\s14\作业>python "3-1 shell sed功能2.1.py" a %

4. 完整代码

# coding=utf-8

import sys

#打开文件

with open('yes.txt','r+',encoding='utf-8') as f1:

    with open('yes2.txt','w',encoding='utf-8') as f_new:

        find_str = sys.argv[1]

        replace_str = sys.argv[2]

        #替换

        for line in f1.readlines():

            line = line.replace(find_str,replace_str).strip()

            print(line)

            f_new.writelines(line)

        f1.close()

        f_new.close()

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