parameters: (files_by_ext, filename)
return_statement: return files_by_ext
docstring: :type files_by_ext: dict
    :type filename: str
    :rtype: dict
docstring_summary: :type files_by_ext: dict
    :type filename: str
    :rtype: dict
docstring_tokens: : type files_by_ext : dict : type filename : str : rtype : dict
function: def SourceFileByExt(files_by_ext, filename):
    """
    :type files_by_ext: dict
    :type filename: str
    :rtype: dict
    """
    ext = os.path.splitext(filename)[-1]
    files_by_ext.setdefault(ext, []).append(filename)
    return files_by_ext
function_tokens: def SourceFileByExt ( files_by_ext , filename ) : ext = os . path . splitext ( filename ) [ - 1 ] files_by_ext . setdefault ( ext , [ ] ) . append ( filename ) return files_by_ext