Replace a Line in Text File

How to replace an entire line in a text file by line number

Not the greatest, but this should work:

sed -i 'Ns/.*/replacement-line/' file.txt

where N should be replaced by your target line number. This replaces the line in the original file. To save the changed text in a different file, drop the -i option:

sed 'Ns/.*/replacement-line/' file.txt > new_file.txt

How to search and replace text in a file?

fileinput already supports inplace editing. It redirects stdout to the file in this case:

#!/usr/bin/env python3
import fileinput

with fileinput.FileInput(filename, inplace=True, backup='.bak') as file:
    for line in file:
        print(line.replace(text_to_search, replacement_text), end='')

Replace String in Specific line in text file

Another approach with Linq

string[] file = File.ReadAllLines(@"c:\yourfile.txt");
file = file.Select((x, i) => i > 1 && i < 5 ? x.Replace("no", "number") : x).ToArray();
File.WriteAllLines(@"c:\yourfile.txt", file);

Replace line in text file using python

As you are reading from the file the file pointer moves as well and it can cause problems. What I would do is first read the file and prepare the "new file" that you want, and then write it into the file, as shown in the code below:

filetest = open ("testingfile.txt", "r")  
lines = filetest.readlines()
filetest.close()
ID = input ("Enter ID: ")
list = ['Hello', 'Testing', 'File', 543210]  
for i in range(len(lines)):
    lines[i] = lines[i].rstrip()
    if ID not in lines[i]:
        continue
    else:
        templine = '\t'.join(map(str, list))
        lines[i] = templine

with open("testingfile.txt", "w") as filetest:
    for line in lines:
        filetest.write(line + "\n")

I didn't change the logic of the code but be aware that if your file has, for example, a line with the number "56" and a line with the number "5", and you enter the ID "5", then the code will replace both of those lines.

Replace line in text file with a new line

First, open the file and save the actual content. Then, replace the string and write the full content back to file.

def remove_line(string)
  # save the content of the file
  file = File.read('test.txt')
  # replace (globally) the search string with the new string
  new_content = file.gsub(string, 'removed succesfully')
  # open the file again and write the new content to it
  File.open('test.txt', 'w') { |line| line.puts new_content }
end

Or, instead of replacing globally:

def remove_line(string)
  file = File.read('test.txt')
  new_content = file.split("\n")
  new_content = new_content.map { |word| word == string ? 'removed succesfully' : word }.join("\n")
  File.open('test.txt', 'w') { |line| line.puts new_content }
end

Python Replace content in specific line at txt file

Instead of that, what you can do is go with this code for editing the text file

with open(path_to_text_file,'r') as txt:
    text=txt.readlines()
    text[3]='phone number\n'

    with open(path_to_text_file,'w') as txt:
        txt.writelines(text)

replace string in specific line in text file in Python

try this out

f1 = open("last_file.txt", 'r+')
f2 = open("output_file.txt", 'w+') 

keyString = '/string_to_search/'
oldString = "any other language"
newString = "python"

f2.write("".join([i.replace(oldString, newString) if keyString in i else i for i in f1.readlines()]))

f1.close()
f2.close()

For example this input file

random line
/string_to_search/ any other language
/string_to_search/ something?

writes the following to the output file:

random line
/string_to_search/ python
/string_to_search/ something?

Replace a line in a text file with any new line using python

Instead of using if statement, using regular expression will help you,

Since you are looking for a specific id followed by the word 'pending', a simple regex : "id=your_id=pending"will work.

Then you can use re.subto replace the entire line by what you want. Here id=your_id=missing/found"

Note : this answer is probably not the best one, since you re-write most of the lines, but for small files, works perfectly.

import re

FILENAME = "textfile.txt"

def update_file(filename,id,word_to_add,lines_to_remove):
    
    lines_to_remove = [s + "\n" for s in lines_to_remove] 
    #adding \n to all lines you want to remove

    pattern =re.compile("^id="+str(id)+"=pending")
    new_lines=[]

    with open(FILENAME,'r+') as  file:

            for line in file:
                if line not in lines_to_remove: # keeping only lines desired

                    new_lines.append(pattern.sub("id=1="+word_to_add,line))

    with open(FILENAME,'w') as  file:
        file.writelines(new_lines)
    
    return 0

update_file(FILENAME,1,"missing",["id=abc2=pending"])

#Output
#id=0=pending
#id=1=missing

           

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