<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def build_from_c_and_cpp_files(extensions):
 """Modify the extensions to build from the .c and .cpp files. This is useful for releases, this way cython is not required to run python setup.py install. """

    for extension in extensions:
        sources = []
        for sfile in extension.sources:
            path, ext = os.path.splitext(sfile)
            if ext in ('.pyx', '.py'):
                if extension.language == 'c++':
                    ext = '.cpp'
                else:
                    ext = '.c'
                sfile = path + ext
            sources.append(sfile)
        extension.sources = sources