How to add an empty line after a certain string within a text file?

Question

I need to find a way to add a new line after a certain string within a text file.

 discount_percent :20 
 discounted :true 
 final_price :1199 
 id :893850 
 name : THELONGING  
 original_price :1499 
 discount_percent :40 
 discounted :true 
 final_price :119 
 id :1476450 
 name : CyberHentai  
 original_price :199 
 discount_percent :30 
 discounted :true 
 final_price :139 
 id :1478030 
 name : MamboWave  
 original_price :199 
 discount_percent :15 
 discounted :true 
 final_price :84 
 id :1506230 
 name : BigfootForest  
 original_price :99 
 discount_percent :40 
 discounted :true 
 final_price :59 
 id :1502600 
 name : AlienX  
 original_price :99

Here I have a .txt file and I need a way to add a new line after any line containing 'original_price' and the price/ numbers after it.

there is probably an easy solution to this but I can't seem to figure this out, and I have practically 0 knowledge of how to use Regex

I have tried the following:

def fixSpacing():
    file1 = open('data.txt', 'w')
    file2 = open('tempdata.txt', 'r+')

    for line in file2.readlines():
        if line.startswith('original_price :'):

But I couldn't think of a way to add a new line after the numbers for price.

You can't write in the middle of a file, you'll have to read the file and write the lines to a new file while checking "if "original_price" in line: line += "\n" — Mick
– Mick, Commented Jan 9, 2021 at 6:53

Daweo · Accepted Answer · 2021-01-09 07:12:58Z

For me it looks like task for built-in module fileinput as it can work in inplace mode. Consider following example, let file.txt content be:

title: 1
price: 100
desc: one
title: 2
price: 200
desc: two

then

import fileinput
for line in fileinput.input("file.txt", inplace=True):
    end = "\n" if line.startswith("price") else ""
    print(line, end=end)

will change said file content to

title: 1
price: 100

desc: one
title: 2
price: 200

desc: two

explanation: in inplace mode standard output is directed to the input file (if a file of the same name as the backup file already exists, it will be replaced silently). This makes it possible to write a filter that rewrites its input file in place. so we can just use print, as input file lines' newlines are preserved using \n as print's end will result in additional empty line and empty str in keeping line unchanged. Keep in mind after using this you will no longer have original file, only altered.

PeacetimeWall22 · Accepted Answer · 2021-01-09 07:08:53Z

1

Thanks, I tinkered around with it for about 10 min and got it to work with the following:

def fixSpacing():
    file1 = open('data.txt', 'w')
    file2 = open('tempdata.txt', 'r+')

    for line in file2.readlines():
        if 'original_price' in line:
            file1.writelines(line + '\n')
        else:
            file1.write(line)

Thanks for the Help.

answered Jan 9, 2021 at 7:08

PeacetimeWall22

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