def import_best(c_module, py_module):
from importlib import import_module<EOL>from os import getenv<EOL>pure_python = getenv("<STR_LIT>", "<STR_LIT>")<EOL>if pure_python:<EOL><INDENT>return import_module(py_module)<EOL><DEDENT>else:<EOL><INDENT>try:<EOL><INDENT>return import_module(c_module)<EOL><DEDENT>except ImportError:<EOL><INDENT>return import_module(py_module)<EOL><DEDENT><DEDENT>
Import the best available module,
    with C preferred to pure Python.