AttributeError: StringIO instance has no attribute 'encoding'

Question

While using PyCharm's interactive console when debugging nosetests, I get the following error:

AttributeError: StringIO instance has no attribute 'encoding'

I found some guidance here, but I don't know how to apply it to my situation.

How can I resolve this issue?

---

Full Stack Trace:

Traceback (most recent call last):
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3.2\helpers\pydev\_pydevd_bundle\pydevd_comm.py", line 1409, in do_it
    result = pydevconsole.console_exec(self.thread_id, self.frame_id, self.expression, dbg)
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3.2\helpers\pydev\pydevconsole.py", line 475, in console_exec
    need_more =  exec_code(CodeFragment(expression), updated_globals, frame.f_locals, dbg)
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3.2\helpers\pydev\pydevconsole.py", line 392, in exec_code
    interpreterInterface = get_interpreter()
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3.2\helpers\pydev\pydevconsole.py", line 372, in get_interpreter
    interpreterInterface = InterpreterInterface(None, None, threading.currentThread())
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3.2\helpers\pydev\_pydev_bundle\pydev_ipython_console.py", line 25, in __init__
    self.interpreter = get_pydev_frontend(host, client_port, show_banner=show_banner)
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3.2\helpers\pydev\_pydev_bundle\pydev_ipython_console_011.py", line 488, in get_pydev_frontend
    _PyDevFrontEndContainer._instance = _PyDevFrontEnd(show_banner=show_banner)
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3.2\helpers\pydev\_pydev_bundle\pydev_ipython_console_011.py", line 318, in __init__
    self.ipython = PyDevTerminalInteractiveShell.instance()
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\traitlets\config\configurable.py", line 412, in instance
    inst = cls(*args, **kwargs)
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\IPython\terminal\interactiveshell.py", line 396, in __init__
    super(TerminalInteractiveShell, self).__init__(*args, **kwargs)
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\IPython\core\interactiveshell.py", line 499, in __init__
    self.init_io()
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\IPython\terminal\interactiveshell.py", line 363, in init_io
    self.enable_win_unicode_console()
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\IPython\terminal\interactiveshell.py", line 357, in enable_win_unicode_console
    stderr=stderr_text_str)
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\win_unicode_console\__init__.py", line 31, in enable
    readline_hook.enable(use_pyreadline=use_pyreadline)
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\win_unicode_console\readline_hook.py", line 134, in enable
    check_encodings()
  File "C:\Users\jimgo\Anaconda2\lib\site-packages\win_unicode_console\readline_hook.py", line 50, in check_encodings
    if sys.stdin.encoding != sys.stdout.encoding:
AttributeError: StringIO instance has no attribute 'encoding'

Answer 1

There's an issue on the JetBrains bug tracker with a solution.

In PyCharm, go to Run > Edit Configurations > Defaults > Python tests > Nosetests. Under Additional arguments put --nocapture. Then delete all the existing test configurations from the top of the left-hand pane.

Try to debug your test again. Don't click the re-test button from the debug panel because this seems to reuse the previous configuration. Instead run the test again by right clicking on the test file for instance.

Answer 2

In case anyone else shows up here... I had a similar stack trace just by using:

import pdb; pdb.set_trace()

In my case it was because I had Django configured with:

TEST_RUNNER = 'xmlrunner.extra.djangotestrunner.XMLTestRunner'

Which was stealing my stdout.