How do I determine if my python shell is executing

Question

I need a way to tell what mode the shell is in from within the shell.

I've tried looking at the platform module but it seems only to tell you about "about the bit architecture and the linkage format used for the executable": the binary is compiled as 64bit though (I'm running on OS X 10.6) so it seems to always report 64bit even though I'm using the methods described here to force 32bit mode).

Answer 1

Grouping everything...

Considering that:

• The question is asked for OSX (I have an old (and cracked) VM with an ancient Python version)
• My main env is Win
• I only have the 32bit version installed on Win (and I built a "crippled" one on Lnx)

I'm going to exemplify on all 3 platforms. I'll be using Python3 and Python2. Doc URLs however, will be Python3 specific.

1. Check [Python 3]: sys.maxsize value - compare it to 0x100000000 (2 ** 32): greater for 64bit, smaller for 32bit:
   • OSX 9 x64:
     • Python 2.7.10 x64:

       >>> import sys
       >>> "Python {:s} on {:s}".format(sys.version, sys.platform)
       'Python 2.7.10 (default, Oct 14 2015, 05:51:29) \n[GCC 4.8.2] on darwin'
       >>> hex(sys.maxsize), sys.maxsize > 0x100000000
       ('0x7fffffffffffffff', True)
       

   • Ubtu 16 x64:
     • Python 3.5.2 x64:

       >>> import sys
       >>> "Python {:s} on {:s}".format(sys.version, sys.platform)
       'Python 3.5.2 (default, Nov 23 2017, 16:37:01) \n[GCC 5.4.0 20160609] on linux'
       >>> hex(sys.maxsize), sys.maxsize > 0x100000000
       ('0x7fffffffffffffff', True)
       

     • Python 3.6.4 x86:

       >>> import sys
       >>> "Python {:s} on {:s}".format(sys.version, sys.platform)
       'Python 3.6.4 (default, Apr 25 2018, 23:55:56) \n[GCC 5.4.0 20160609] on linux'
       >>> hex(sys.maxsize), sys.maxsize > 0x100000000
       ('0x7fffffff', False)
       

   • Win 10 x64:
     • Python 3.5.4 x64:

       >>> import sys
       >>> "Python {:s} on {:s}".format(sys.version, sys.platform)
       'Python 3.5.4 (v3.5.4:3f56838, Aug  8 2017, 02:17:05) [MSC v.1900 64 bit (AMD64)] on win32'
       >>> hex(sys.maxsize), sys.maxsize > 0x100000000
       ('0x7fffffffffffffff', True)
       

     • Python 3.6.2 x86:

       >>> import sys
       >>> "Python {:s} on {:s}".format(sys.version, sys.platform)
       'Python 3.6.2 (v3.6.2:5fd33b5, Jul  8 2017, 04:14:34) [MSC v.1900 32 bit (Intel)] on win32'
       >>> hex(sys.maxsize), sys.maxsize > 0x100000000
       ('0x7fffffff', False)
       

2. Use [Python 3]: struct.calcsize(fmt) to determine the object size produced by the (pointer) format. In other words, determines the pointer size (sizeof(void*)):
   • OSX 9 x64:
     • Python 2.7.10 x64:

       >>> import struct
       >>> truct.calcsize("P") * 8
       64
       

   • Ubtu 16 x64:
     • Python 3.5.2 x64:

       >>> import struct
       >>> truct.calcsize("P") * 8
       64
       

     • Python 3.6.4 x86:

       >>> import struct
       >>> truct.calcsize("P") * 8
       32
       

   • Win 10 x64:
     • Python 3.5.4 x64:

       >>> import struct
       >>> truct.calcsize("P") * 8
       64
       

     • Python 3.6.2 x86:

       >>> import struct
       >>> truct.calcsize("P") * 8
       32
       

3. Use [Python 3.5]: ctypes - A foreign function library for Python. It also boils down to determining the size of a pointer (sizeof(void*)). As a note, ctypes uses #2. (not necessarily for this task) via "${PYTHON_SRC_DIR}/Lib/ctypes/__init__.py" (around line #15):
   • OSX 9 x64:
     • Python 2.7.10 x64:

       >>> import ctypes
       >>> ctypes.sizeof(ctypes.c_void_p) * 8
       64
       

   • Ubtu 16 x64:
     • Python 3.5.2 x64:

       >>> import ctypes
       >>> ctypes.sizeof(ctypes.c_void_p) * 8
       64
       

     • Python 3.6.4 x86:

       >>> import ctypes
       >>> ctypes.sizeof(ctypes.c_void_p) * 8
       32
       

   • Win 10 x64:
     • Python 3.5.4 x64:

       >>> import ctypes
       >>> ctypes.sizeof(ctypes.c_void_p) * 8
       64
       

     • Python 3.6.2 x86:

       >>> import ctypes
       >>> ctypes.sizeof(ctypes.c_void_p) * 8
       32
       

4. [Python 3]: platform.architecture(executable=sys.executable, bits='', linkage='') !!! NOT reliable on OSX !!! due to multi arch executable (or .dylib) format (in some cases, uses #2.):
   • OSX 9 x64:
     • Python 2.7.10 x64:

       >>> import platform
       >>> platform.architecture()
       ('64bit', '')
       

   • Ubtu 16 x64:
     • Python 3.5.2 x64:

       >>> import platform
       >>> platform.architecture()
       ('64bit', 'ELF')
       

     • Python 3.6.4 x86:

       >>> import platform
       >>> platform.architecture()
       ('32bit', 'ELF')
       

   • Win 10 x64:
     • Python 3.5.4 x64:

       >>> import platform
       >>> platform.architecture()
       ('64bit', 'WindowsPE')
       

     • Python 3.6.2 x86:

       >>> import platform
       >>> platform.architecture()
       ('32bit', 'WindowsPE')
       

5. Lame workaround (gainarie) - invoke an external command ([man7]: FILE(1)) via [Python 3]: os.system(command). The limitations of #4. apply (sometimes it might not even work):
   • OSX 9 x64:
     • Python 2.7.10 x64:

       >>> import os
       >>> os.system("file {:s}".format(os.path.realpath(sys.executable)))
       /opt/OPSWbuildtools/2.0.6/bin/python2.7.global: Mach-O 64-bit executable x86_64
       

   • Ubtu 16 x64:
     • Python 3.5.2 x64:

       >>> import os
       >>> os.system("file {:s}".format(os.path.realpath(sys.executable)))
       /usr/bin/python3.5: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=59a8ef36ca241df24686952480966d7bc0d7c6ea, stripped
       

     • Python 3.6.4 x86:

       >>> import os
       >>> os.system("file {:s}".format(os.path.realpath(sys.executable)))
       /home/cfati/Work/Dev/Python-3.6.4/python: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=5c3d4eeadbd13cd91445d08f90722767b0747de2, not stripped
       

   • Win 10 x64:
     • file utility is not present, there are other 3^rd Party tools that can be used, but I'm not going to insist on them

Win specific:

6. Check env vars (e.g. %PROCESSOR_ARCHITECTURE% (or others)) via [Python 3]: os.environ:
   • Win 10 x64:
     • Python 3.5.4 x64:

       >>> import os
       >>> os.environ["PROCESSOR_ARCHITECTURE"]
       'AMD64'
       

     • Python 3.6.2 x86:

       >>> import os
       >>> os.environ["PROCESSOR_ARCHITECTURE"]
       'x86'
       

7. [Python 3]: sys.version (also displayed in the 1^st line when starting the interpreter)
   • Check #1.