Question

How can you tell whether python has been started with the -i flag?

According to the docs, you can check the PYTHONINSPECT variable in os.environ, which is the equivalent of -i. But apparently it doesn’t work the same way.

Works:

$ PYTHONINSPECT=1 python -c 'import os; print os.environ['PYTHONINSPECT']' 

Doesn’t work:

$ python -i -c 'import os; print os.environ['PYTHONINSPECT']' 

The reason I ask is because I have a script that calls sys.exit(-1) if certain conditions fail. This is good, but sometimes I want to manually debug it using -i. I suppose I can just learn to use ‘PYTHONINSPECT=1 python’ instead of ‘python -i’, but it would be nice if there were a universal way of doing this.

Answer 1

How to set inspect mode programmatically

The answer from the link @Jweede provided is imprecise. It should be:

import os os.environ['PYTHONINSPECT'] = '1' 

How to retrieve whether interactive/inspect flags are set

Just another variant of @Brian’s answer:

import os from ctypes import POINTER, c_int, cast, pythonapi  def in_interactive_inspect_mode():     '''Whether '-i' option is present or PYTHONINSPECT is not empty.'''     if os.environ.get('PYTHONINSPECT'): return True     iflag_ptr = cast(pythonapi.Py_InteractiveFlag, POINTER(c_int))     #NOTE: in Python 2.6+ ctypes.pythonapi.Py_InspectFlag > 0     #      when PYTHONINSPECT set or '-i' is present      return iflag_ptr.contents.value != 0 

See the Python’s main.c.