搜索单词，并使用 fileinput 在 Python 文件中替换包含该单词的整行

Question

I want to search a particular word in a text file. For each line,where the word is present, I want to completely change the line by a new text.

I want to achieve this using fileinput module of python. There are two observation, I am seeing with following variations:-

Code piece 1:-

text = "mov9 = "   # if any line contains this text, I want to modify the whole line.
new_text = "mov9 = Alice in Wonderland"
x = fileinput.input(files="C:\Users\Admin\Desktop\DeletedMovies.txt", inplace=1)
for line in x:
    if text in line:
        line = new_text
        print line,
x.close()

The above piece of code wipes out all the content of the file, and writes the new_text ie the file content is only

mov9 = Alice in Wonderland

Code Piece 2:-

text = "mov9 = "   # if any line contains this text, I want to modify the whole line.
new_text = "mov9 = Alice in Wonderland"
x = fileinput.input(files="C:\Users\Admin\Desktop\DeletedMovies.txt", inplace=1)
for line in x:
    if text in line:
        line = line.replace(text, new_text)
        print line,
x.close()

The above piece of code, even though adds the needed line ie new_text where text is found, but doesn't deletes the line, but keeps the previous data also.

That is if the line was earlier:-

mov9 = Fast & Furios

after running the above piece of code it becomes:-

mov9 = Alice in WonderlandFast & Furios

And other content of the files remain untouched, not deleted as in code in Code piece 1.

But my goal is to find the word mov9 = , and whatever is present along with it, I want to replace the whole line as mov9 = Alice in Wonderland .

How can I achieve that? Thanks in advance....

Answer 1

I realized that I was wrong by just an indentation. In the code piece 1 mentioned in the question, if I am bringing the 'print line,' from the scope of if ie if i outdent it, then this is solved...

As this line was inside the scope of if , hence, only this new_text was being written to the file, and other lines were not being written, and hence the file was left with only the new_text . So, the code piece should be as follow:-

text = "mov9 = "   # if any line contains this text, I want to modify the whole line.
new_text = "mov9 = Alice in Wonderland"
x = fileinput.input(files="C:\Users\Admin\Desktop\DeletedMovies.txt", inplace=1)
for line in x:
    if text in line:
        line = new_text
    print line,
x.close()

Also, the second solution given by Rolf of Saxony & the first solution by Padraic Cunningham is somehow similar.

Answer 2

You empty you file because you only write when you find a match, you need to always write the lines:

import sys

text = "mov9 = "   # if any line contains this text, I want to modify the whole line.
new_text = "mov9 = Alice in Wonderland\n"

x = fileinput.input(files="C:\Users\Admin\Desktop\DeletedMovies.txt", inplace=1)
for line in x:
    if text in line:
        line = new_text
    sys.stdout.write(line)

If you find a match the line will be set to new_text , so either sys.stdout.write(line) will write the original line or new_text . Also if you actually want to find lines starting with text use if line.startswith(text):

You could also write to a tempfile and replace the original:

from shutil import move
from tempfile import NamedTemporaryFile

text = "mov9 = "   # if any line contains this text, I want to modify the whole line.
new_text = "mov9 = Alice in Wonderland\n"

with open("C:\Users\Admin\Desktop\DeletedMovies.txt") as f, NamedTemporaryFile("w", dir=".", delete=False) as tmp:
    for line in f:
        if text in line:
            line = new_text
        tmp.write(line)


move(tmp.name, "C:\Users\Admin\Desktop\DeletedMovies.txt")

Answer 3

As vyscond suggested:

import re
yourTxt = ''.join(open('file.txt').readlines())
yourTxt = re.sub(r'\bmov9\b', r'mov9 = Alice in Wonderland', yourTxt)

#Save the new text on disk
f = open('newTxt.txt', 'w')
f.write(yourTxt)
f.close()

Answer 4

I would suggest use two file simultaneously to replace the text and write the replaced data in another file and simply delete the older file.

path="Hello.txt"
path2="Hello2.txt"
file1_open=open(path,"r") 
file2_open=open(path2,"w")
for line in file1_open:
if "a" in line:
print "found"
    line=line.replace('a',"replaced")
print line
    file2_open.write(line)

Now you can internally delete the file1_open file. It's small and simple though may take load on CPU when with large files.

Answer 5

It looks like this may not be the only solution on this theme, now that I have re-read the answers but as I knocked the code up here goes. Keep it simple:

import os
text = "mov9 = "   # if any line contains this text, I want to modify the whole line.
new_text = "mov9 = Alice in Wonderland "
new=open("new.txt",'w')
with open('DeletedMovies.txt', 'r') as f:
    for line in f.readlines():
        if text in line:
            line = line.replace(text, new_text)
            print line
        new.write(line)
new.close()
os.rename('DeletedMovies.txt', 'DeletedMovies.txt.old')
os.rename('new.txt', 'DeletedMovies.txt')

It rather depends on just how big you expect this file to get.

Edit: If you are determined to use fileinput despite the the fact that it will be confusing for anyone unfamiliar with that package, as it is not at all clear what is happening, then you were almost there with your existing code.
The following should work:

import fileinput
text = "mov9 = "   # if any line contains this text, I want to modify the whole line.
new_text = "mov9 = Alice in Wonderland "

for line in fileinput.input("DeletedMovies.txt", inplace = 1):
    if text in line:
        print line.replace(line,new_text)
    else:
        print line.strip()

Answer 6

With a slight improvement to the Rolf of Saxony answer, this you can run the script without having to hard coded values.

import fileinput
import sys

filename=sys.argv[1]
old_value=sys.argv[2]
new_value=sys.argv[3]

with fileinput.FileInput(filename, inplace=True, backup='.bak') as file:
    for line in file:
        if old_value in line:
            print(line.replace(line,new_value))
        else:
            print(line.strip())

Now run it as replace.py filename.txt old_value New_Value from the command line