title: Can't import os.listdir
body: <p>I have a quick question.
  I try to import 'os.listdir' with </p>
  
  <pre><code>import os.listdir
  </code></pre>
  
  <p>However, it shows me an error like below.</p>
  
  <pre><code>Exception has occurred: ModuleNotFoundError
  No module named 'os.listdir'; 'os' is not a package
  
    File "/Users/chanwooahn/Google Drive/Projects/The Economist/main.py", line 1, in
  
   &lt;module&gt;import os.listdir
  
    File "/anaconda3/lib/python3.6/runpy.py", line 85, in _run_code
      exec(code, run_globals)
  
    File "/anaconda3/lib/python3.6/runpy.py", line 96, in _run_module_code
      mod_name, mod_spec, pkg_name, script_name)
  
    File "/anaconda3/lib/python3.6/runpy.py", line 263, in run_path
      pkg_name=pkg_name, script_name=fname)
  </code></pre>
  
  <p>I thought 'os' is a built-in interface of python.
  I have updated 'conda' and 'python', but still, it gave me the same error.
  Is there any possible reason for this?</p>