Merging lines in Notepad++ or by using Python

Question

I have a long file which is structured like below:

• every line should start with 500
• there are lines not starting with 500 (Line 2, Line 4, basically every even line)

What I want to do:

• The lines not starting with 500 should be merged with not even line above (so Line 2 with Line 1, Line 4 with Line 3, etc).
• Once merging additional semicolon should be added (i.e. <Line 1>;<Line 2>).

How I can easily do it in python (2.7)?

Regex in Notepad++ may also work. I've heard that I should use a multi-line mode but I don't know how to do it. Probably it's not even hard but I have a hard time dealing with it.

Thanks.

Here the input (simplified):

;500;616;;”YPO_INV”;”KP”;”51D0072”;”YNU”
;”     6,291.00”;;
;500;6900;;”YPNV”;”KE”;”53213072”;”YOU”
;”     6,991.00”;;

Expected output:

;500;616;;”YPO_INV”;”KP”;”51D0072”;”YNU”;;”     6,291.00”;;
;500;6900;;”YPNV”;”KE”;”53213072”;”YOU”;;”     6,991.00”;;

Answer 1

Regex: \n^(?!;500)

Details:

• ^ Asserts position at start of a line
• (?!) Negative Lookahead

Python code:

text = open(r'C:\....txt').read()
r = re.compile(r'\n^(?!;500)', re.M)
text = r.sub(';', text)

Output:

;500;616;;”YPO_INV”;”KP”;”51D0072”;”YNU”;;”     6,291.00”;;
;500;6900;;”YPNV”;”KE”;”53213072”;”YOU”;;”     6,991.00”;;

Demo code

Answer 2

Use Notepad++ for this kind of simple changes.

1. Go to Replace menu (Ctrl+H)
2. Select Regular expressions (Alt+G)

3. Enter following values:

   • Find what: [\r\n]+(;(?!500))
   • Replace with: \1

4. Click on Replace All (Alt+A)

Answer 3

Try this regex:

[\r\n]+(?!;500)

Replace each match with a ;

Click for Demo

Explanation:

• [\r\n]+ - matches 1+ occurrences of either a newline character or a carriage return
• (?!;500) - negative lookahead to make sure that the current position is not followed by :500

Before Replacing:

After replacing: