CODEWITHSUNDEEP
python
Nemo
Nemo

Reputation: 111

Python: How to open a file and comment a particular line?

Is there a way to open a file (let's say a .py file) and comment a particular line already existent in the file? Or is there a way to create a piece of code that replaces that line with another one?

Upvotes: 0

Views: 1101

Answers (3)

Nihal Sangeeth
Nihal Sangeeth

Reputation: 5535

Yes. You can open a file and read it line by line as,

with open('file.py') as f:
    lines = f.readlines()

Search for the particular line as raw string or regular expression with an if condition and replace it like,

for n, line in enumerate(lines):
    if(line == search_line):
        lines[n] = new_line

Write to the same file like:

with open('file.py', 'w') as f:
    f.write(''.join(lines))

Upvotes: 1

nerd100
nerd100

Reputation: 97

Here is a python solution that takes a file called commentFile.py and comments out any line containing the string comment.

wfile = open("commentFile.py","r+")

d = wfile.readlines()
wfile.seek(0)
allLines = []

for line in d:
    if("comment" in line and "#" not in line):
        allLines.append("#"+line)
    else:
        allLines.append(line)
wfile.writelines(allLines)
wfile.close()

Upvotes: 0

Igl3
Igl3

Reputation: 5108

How about just read in the file line by line and then append to an output file the lines either with or without a comment, depending on your needs.

For example to add the comment on each line starting with the string abc you could do:

with open('in.txt', 'a') as outfile:
    with open('test.txt', 'r') as infile:
        for line in infile.readlines():
            if line.startswith('abc'):
                outfile.write(line.strip() + " # Here's abc\n")
            else:
                outfile.write(line)

This would make:

abc 1 # Here's abc
blabla 2
def 3
abc 4 # Here's abc

from the input file:

abc 1
blabla 2
def 3
abc 4

The check wether a line needs commented can also be searching by regex or by modifying my example a bit you could comment also certain line numbers. But that's up to you now to figure out.

Upvotes: 1

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