Don't use stdout/stderr directly for python output

Python interpreter commands use the builtin InteactiveConsole which interacts with stdout and stderr directly. This isn't a problem for our tor-prompt since it writes to stdout anyway, but it breaks nyx. Nicest option I've found for this is... https://stackoverflow.com/questions/13250050/redirecting-the-output-of-a-python-function-from-stdout-to-variable-in-python

Don't use stdout/stderr directly for python output
ae48d813 · Damian Johnson · e1cb6914 · ae48d813
Commit ae48d813 authored Jul 31, 2016 by Damian Johnson
--- a/stem/interpreter/commands.py
+++ b/stem/interpreter/commands.py
@@ -6,7 +6,9 @@ Handles making requests and formatting the responses.
 """

 import code
+import contextlib
 import socket
+import sys

 import stem
 import stem.control
@@ -19,6 +21,11 @@ import stem.util.tor_tools
 from stem.interpreter import STANDARD_OUTPUT, BOLD_OUTPUT, ERROR_OUTPUT, uses_settings, msg
 from stem.util.term import format

+try:
+  from cStringIO import StringIO
+except ImportError:
+  from io import StringIO
+

 def _get_fingerprint(arg, controller):
  """
@@ -84,6 +91,17 @@ def _get_fingerprint(arg, controller):
    raise ValueError("'%s' isn't a fingerprint, nickname, or IP address" % arg)


+@contextlib.contextmanager
+def redirect(stdout, stderr):
+  original = sys.stdout, sys.stderr
+  sys.stdout, sys.stderr = stdout, stderr
+
+  try:
+    yield
+  finally:
+    sys.stdout, sys.stderr = original
+
+
 class ControlInterpreter(code.InteractiveConsole):
  """
  Handles issuing requests and providing nicely formed responses, with support
@@ -338,8 +356,13 @@ class ControlInterpreter(code.InteractiveConsole):
        is_tor_command = cmd in config.get('help.usage', {}) and cmd.lower() != 'events'

        if self._run_python_commands and not is_tor_command:
+          console_output = StringIO()
+
+          with redirect(console_output, console_output):
            self.is_multiline_context = code.InteractiveConsole.push(self, command)
-          return
+
+          output = console_output.getvalue()
+          return output if output else None
        else:
          try:
            output = format(self._controller.msg(command).raw_content().strip(), *STANDARD_OUTPUT)