<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _add_defaults_python(self):
 """getting python files"""

        if self.distribution.has_pure_modules():
            build_py = self.get_finalized_command('build_py')
            self.filelist.extend(build_py.get_source_files())
            # This functionality is incompatible with include_package_data, and
            # will in fact create an infinite recursion if include_package_data
            # is True.  Use of include_package_data will imply that
            # distutils-style automatic handling of package_data is disabled
            if not self.distribution.include_package_data:
                for _, src_dir, _, filenames in build_py.data_files:
                    self.filelist.extend([os.path.join(src_dir, filename)
                                          for filename in filenames])