Python script to insert lines in multiple files following a pattern

In the past days I had to build a script to insert some lines of code after a specific statement.
For example, I have the following file:

    a > b
    a = foo(c)
    b = 2
    b = foo(b)
    foo
    bar
    foobar
    b = foo(v)

And I need to add a line variable = bar(42) after every line of variable = foo(x)

After that treatment my file would be like this:

    a > b
    a = foo(c)
    a = bar(42)
    b = 2
    b = foo(b)
    b = bar(42)
    foo
    bar
    foobar
    c = foo(v)
    c = bar(42)

Also, I had to perform this task on multiple files at the same time, the files are listed in a visual studio search result that will look like this:

    Find all "foo(", Subfolders, Find Results 1, "c:\", "*.txt"
      C:\file1.txt(2):a = foo(c)
      C:\file1.txt(4):b = foo(b)
      C:\file1.txt(8):c = foo(v)
      C:\file2.txt(2):a1 = foo(c)
      C:\file2.txt(4):a3 = foo(b)
      C:\file2.txt(8):variable1 = foo(v)
      Matching lines: 6    Matching files: 2    Total files searched: 214
      Find was stopped in progress.

So we need a way to get the set of files from the visual studio search result and then run the task on each of them.

Here is the main algorithm where:

• LINE_TO_INSERT is the line to insert, in this case = bar(42)\n
• PATTERN_OF_LINE in the pattern after which we insert the line
  In this case '\w+' + '\\ \\=\\ foo\\(' + '\w+' which matches with a = foo(b) for example
• PATTERN_OF_FILE is the pattern of the files we are looking for in the visual studio search result

The main function is insert_in_files().

    def insert_in_files():
    	'''Insert LINE_TO_INSERT after all lines with pattern PATTERN_OF_LINE in all files with PATTERN_OF_FILE'''
    	files = get_files('vs_search_output.txt')
    	for f in files:
    		insert_lines(f)
    	return None

Build a set of files from a visual studio search result:

Here is the code that will get the set of files in the search result.
Where PATTERN_OF_FILE is equal to 'C\\:\\\\\w+.txt'. Which means any files with extension .txt whose name is any word character.

    def get_files(path):
    	'''Return a set of files from a visual studio search output following a regexp pattern
    	
    	Format of visual studio search output is the following:
    	Find all "pattern to search", Subfolders, Find Results 1, Entire Solution, ""
    	  path_to_file.txt(1):		line with text
    	  path_to_another_file.txt(22):		line1 some text
    	  path_to_another_file.txt(29):		line2 some text
    	Matching lines: 2    Matching files: 2    Total files searched: 205
    	
    	Args:
    		path: A path to a file with the search result
    		
    	Returns:
    		A set of all files in search result that match PATTERN_OF_FILE regular expression.
    	'''
    	from re import search
    	from re import escape
    
    	f = open(path, 'r')
    	# paths is a set structure with all the different files to look for.
    	paths = set()
    	count = 0
    	for line in f:
    		m = search(PATTERN_OF_FILE, line)
    		if m:
    			paths.add(m.group(0))
    	f.close()
    	return paths

If you run this function you will get a set of files.

• insert_in_files is the python file where the get_files is located.
• vs_search_output.txt is the visual studio search result listed above.

In a python shell:

    >>> import insert_in_files
    >>> insert_in_files.get_files("vs_search_output.txt")
    {'C:\\file1.txt', 'C:\\file2.txt'}
    >>>

Search for pattern in file and insert a line:

As a remainder here are the constants we use:

    PATTERN_OF_FILE = 'C\\:\\\\\w+.txt'
    PATTERN_OF_LINE = '\w+' + '\\ \\=\\ foo\\(' + '\w+' 	# looking for pattern a = foo(b)
    FIRST_VAR = '^\w+'
    LINE_TO_INSERT = ' = bar(42)\n'

And here is the code to search in a file and insert a line:

    	'''Insert a line with 'FIRST_VAR + LINE_TO_INSERT' after each PATTERN_OF_LINE
    	
    	Go through a file looking for PATTERN_OF_LINE 
    	if found, insert a line just after with 'FIRST_VAR + LINE_TO_INSERT'
    	
    	Args:
    		path: a path to a file to search and insert lines if a match is found
    	Returns:
    		None
    	'''
    	from re import escape
    	from re import search
    	fin = open(path, 'r')
    	open('output', 'w').close() 	# clear file before processing
    	fout = open('output', 'w')
    	
    	for line in fin:
    		fout.write(line)
    		match = search(PATTERN_OF_LINE, line)
    		if match:
    			res = search(FIRST_VAR, line)
    			if res:
    				fout.write(res.group(0) + LINE_TO_INSERT)
    	fin.close()
    	fout.close()
    	# save file
    	ftemp = open('output', 'r')
    	try:
    		open(path, 'w').close() 	# clear file before processing
    	except:
    		print('cannot write in file:', path)
    		ftemp.close()
    		return None
    	f = open(path, 'w')
    	for line in ftemp:
    		f.write(line)
    	f.close()
    	ftemp.close()
    	return None

I made a gist with all the files and scripts.
Santiaago