How to delete the commas at the previous line before specific string by PYTHON

Question

I'm dealing with a tough question. I need to delete some commas at the end of the line, which is previous some specific strings.

Such as:

define{
   varA,
   varB,
   varC
}

The specific string is varC, and I want to delete varC and the comma(,) after varB at the same time.

The modified text is

define{
   varA,
   varB
}

I must deal with many code files so I need a script to do it, but that's tough for me.

Answer 1

You could use a regex that looks for the define blocks, separating them in 3 groups:

• the first one starting with define{... and taking everything afterwards non-greedily, including newlines (so we'll need the re.DOTALL flag to allow . to match newlines)
• the second one is the part we want to remove: a comma, some space, some word
• the third one is the final spaces and closing }

We just have to use re.sub to replace the matches by the first and third groups only:

data = """ 
some code
some more code
define{
   varA,
   varB,
   varC
}
some code
define{
   varD,
   varE
}
end of code
"""

import re

define_re = re.compile(r'(define{.*?)(,\s+\w+)(\s+})', re.DOTALL)
out = define_re.sub(r'\1\3', data)

print(out)

Output:

some code
some more code
define{
   varA,
   varB
}
some code
define{
   varD
}
end of code