tell whether python is in -i mode

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 eq

Answer 1

I took a look at the source, and although the variable set when -i is provided is stored in Py_InteractiveFlag, it doesn't look like it gets exposed to python.

However, if you don't mind getting your hands a bit dirty with some low-level ctypes inspecting, I think you can get at the value by:

import ctypes, os

def interactive_inspect_mode():
    flagPtr = ctypes.cast(ctypes.pythonapi.Py_InteractiveFlag, 
                         ctypes.POINTER(ctypes.c_int))
    return flagPtr.contents.value > 0 or bool(os.environ.get("PYTHONINSPECT",False))

[Edit] fix typo and also check PYTHONINSPECT (which doesn't set the variable), as pointed out in comments.