Merge Latex files while working in individual files

file_1.tex

% Many Latex configurations

\begin{document}

\section{File 1}

\end{document}

file_2.tex

% Many Latex configurations

\begin{document}

\section{File 2}

\end{document}

main.tex

% Many Latex configurations

\begin{document}

\input{./merged.tex}

\end{document}

Merge_latex_files.py

import re

def file_get_contents(filename):
    with open(filename) as f:
        return f.read()
def file_put_contents(filename, data):
    with open(filename, 'w') as f:
        f.write(data)
        f.close()

files = [
    './file_1.tex',
    './file_2.tex',
]
merge = ''

for _file in files:
    a = file_get_contents(_file)
    m = re.match(r'[\s\S]*begin\{document\}([\s\S]*)\\end\{document\}', a)
    if (m):
        merge += m.group(1)
    else:
        print('Document content not found.')

file_put_contents('./merged.tex', merge)