CODEWITHSUNDEEP
pythonlistfile-io
Mansueli
Mansueli

Reputation: 6949

python remove "many" lines from file

I am trying to remove specific line numbers from a file in python in a way such as

./foo.py filename.txt 4 5 2919

Where 4 5 and 2919 are line numbers

What I am trying to do is:

for i in range(len(sys.argv)):
    if i>1: # Avoiding sys.argv[0,1]
        newlist.append(int(sys.argv[i]))

Then:

count=0

generic_loop{ 
   bar=file.readline()
   count+=1
   if not count in newlist:
      print bar
}

it prints all the lines in original file (with blank spaces in between)

Upvotes: 2

Views: 253

Answers (4)

jamylak
jamylak

Reputation: 133574

The fileinput module has an inplace=True option that redirects stdout to a tempfile which is automatically renamed after for you.

import fileinput
exclude = set(map(int, sys.argv[2:]))

for i, line in enumerate(fileinput.input('filename.txt', inplace=True), start=1):
    if i not in exclude:
        print line, # fileinput inplace=True redirects stdout to tempfile

Upvotes: 1

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 250961

You can try something like this:

import sys
import os
filename= sys.argv[1]
lines = [int(x) for x in sys.argv[2:]]

#open two files one for reading and one for writing

with open(filename) as f,open("newfile","w") as f2:

#use enumerate to get the line as well as line number, use enumerate(f,1) to start index from 1
    for i,line in enumerate(f):  
        if i not in lines:     #`if i not in lines` is more clear than `if not i in line`
            f2.write(line)   
os.rename("newfile",filename)  #rename the newfile to original one

Note that for the generation of temporary files it's better to use tempfile module.

Upvotes: 2

phihag
phihag

Reputation: 287885

You can use enumerate to determine the line number:

import sys
exclude = set(map(int, sys.argv[2:]))
with open(sys.argv[1]) as f:
    for num,line in enumerate(f, start=1):
        if num not in exclude:
            sys.stdout.write(line)

You can remove start=1 if you start counting at 0. In the above code, the line numbering starts with 1:

$ python3 so-linenumber.py so-linenumber.py 2 4 5
import sys
with open(sys.argv[1], 'r') as f:
            sys.stdout.write(line)

If you want to write the content to the file itself, write it to a temporary file instead of sys.stdout, and then rename that to the original file name (or use sponge on the command-line), like this:

import os
import sys
from tempfile import NamedTemporaryFile
exclude = set(map(int, sys.argv[2:]))
with NamedTemporaryFile('w', delete=False) as outf:
    with open(sys.argv[1]) as inf:
        outf.writelines(line for n,line in enumerate(inf, 1) if n not in exclude)
    os.rename(outf.name, sys.argv[1])

Upvotes: 3

Francis Avila
Francis Avila

Reputation: 31621

import sys
# assumes line numbering starts with 1
# enumerate() starts with zero, so we subtract 1 from each line argument
omitlines = set(int(arg)-1 for arg in sys.argv[2:] if int(arg) > 0)
with open(sys.argv[1]) as fp:
    filteredlines = (line for n,line in enumerate(fp) if n not in omitlines)
    sys.stdout.writelines(filteredlines)

Upvotes: 2

Related Questions