Backspace and add comma before keyword in python

I need to backspace and add a comma right before every instance of 'https:' in a file. I believe regular expression can do this but i'm not sure how.

The line below is what I would like.

2021-05-11 23:39:30,https://www.tiktokv.com/share/video/

Current format is this:

2021-05-11 23:35:41
https://www.tiktokv.com/share/video/

Solution

Using Regex with pattern r"(\n)(?=https)"

Ex:

s = """2021-05-11 23:35:41
https://www.tiktokv.com/share/video/
2021-05-11 23:35:41
https://www.tiktokv.com/share/video/
2021-05-11 23:35:41
https://www.tiktokv.com/share/video/"""

print(re.sub(r"(\n)(?=https)", r",", s))

Output:

2021-05-11 23:35:41,https://www.tiktokv.com/share/video/
2021-05-11 23:35:41,https://www.tiktokv.com/share/video/
2021-05-11 23:35:41,https://www.tiktokv.com/share/video/

Without regex

from io import StringIO
s = StringIO("""2021-05-11 23:35:41
https://www.tiktokv.com/share/video/
2021-05-11 23:35:41
https://www.tiktokv.com/share/video/
2021-05-11 23:35:41
https://www.tiktokv.com/share/video/""")

res = []

for idx, line in enumerate(s, 1):
    if idx % 2 == 0:
        res[-1] += f',{line}'
    else:
        res.append(line.strip())
print(res)

Output:

['2021-05-11 23:35:41,https://www.tiktokv.com/share/video/\n',
 '2021-05-11 23:35:41,https://www.tiktokv.com/share/video/\n',
 '2021-05-11 23:35:41,https://www.tiktokv.com/share/video/']