How do I determine if my python shell is executing in 32bit or 64bit

Question

I need a way to tell what mode the shell is in from within the shell  While I m primarily an OS X user  I d be interested in knowing about other platforms as well  I ve tried looking at the platform module but it seems only to tell you about  quot about the bit architecture and the linkage format used for the executable quot   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

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import sys print sys version    3 5 1  v3 5 1 37a07cee5969  Dec  6 2015  01 54 25   MSC v 1900 64 bit  AMD64

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One way is to look at sys maxsize as documented here     python-32 -c  import sys print   x    sys maxsize  sys maxsize  gt  2  32     7fffffff   False    python-64 -c  import sys print   x    sys maxsize  sys maxsize  gt  2  32     7fffffffffffffff   True    sys maxsize was introduced in Python 2 6   If you need a test for older systems  this slightly more complicated test should work on all Python 2 and 3 releases     python-32 -c  import struct print  8   struct calcsize  P     32   python-64 -c  import struct print  8   struct calcsize  P     64   BTW  you might be tempted to use platform architecture   for this   Unfortunately  its results are not always reliable  particularly in the case of OS X universal binaries     arch -x86 64  usr bin python2 6 -c  import sys platform  print platform architecture   0   sys maxsize  gt  2  32  64bit True   arch -i386  usr bin python2 6 -c  import sys platform  print platform architecture   0   sys maxsize  gt  2  32  64bit False

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Open python console   import platform platform architecture   0    it should display the  64bit  or  32bit  according to your platform   Alternatively  in case of OS X binaries     import sys sys maxsize  gt  2  32    it should display True in case of 64bit and False in case of 32bit

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platform architecture   notes say      Note    On Mac OS X  and perhaps other platforms   executable files may be universal files containing multiple architectures       To get at the    64-bitness    of the current interpreter  it is more reliable   to query the sys maxsize attribute    import sys is 64bits   sys maxsize  gt  2  32

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On Windows OS Open the cmd termial and start python interpreter by typing  gt python as shown in the below image  If the interpreter info at start contains AMD64  it s 64-bit  otherwise  32-bit bit

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struct calcsize  P   returns size of the bytes required to store a single pointer  On a 32-bit system  it would return 4 bytes  On a 64-bit system  it would return 8 bytes    So the following would return 32 if you re running 32-bit python and 64 if you re running 64-bit python   Python 2  import struct print struct calcsize  P     8   Python 3  import struct print struct calcsize  P     8

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Basically a variant on Matthew Marshall s answer  with struct from the std library    import struct print struct calcsize  P     8

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Do a python -VV in the command line  It should return the version

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Platform Architecture is not the reliable way  Instead us     arch -i386  usr local bin python2 7 Python 2 7 9  v2 7 9 648dcafa7e5f  Dec 10 2014  10 10 46   GCC 4 2 1  Apple Inc  build 5666   dot 3   on darwin Type  help    copyright    credits  or  license  for more information   gt  gt  gt  import platform  sys  gt  gt  gt  platform architecture    sys maxsize    64bit        2147483647   gt  gt  gt   D   arch -x86 64  usr local bin python2 7 Python 2 7 9  v2 7 9 648dcafa7e5f  Dec 10 2014  10 10 46   GCC 4 2 1  Apple Inc  build 5666   dot 3   on darwin Type  help    copyright    credits  or  license  for more information   gt  gt  gt  import platform  sys  gt  gt  gt  platform architecture    sys maxsize    64bit        9223372036854775807

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Try using ctypes to get the size of a void pointer   import ctypes print ctypes sizeof ctypes c voidp    It ll be 4 for 32 bit or 8 for 64 bit

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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  using Python 3 and Python 2    Check  Python 3 Docs   sys maxsize value - compare it to 0x100000000  2    32   greater for 64bit  smaller for 32bit    OSX 9 x64    Python 2 7 10 x64     gt  gt  gt  import sys  gt  gt  gt   Python  0 s  on  1 s   format sys version  sys platform   Python 2 7 10  default  Oct 14 2015  05 51 29   n GCC 4 8 2  on darwin   gt  gt  gt  hex sys maxsize   sys maxsize  gt  0x100000000   0x7fffffffffffffff   True     Ubuntu 16 x64    Python 3 5 2 x64     gt  gt  gt  import sys  gt  gt  gt   Python  0 s  on  1 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   gt  gt  gt  hex sys maxsize   sys maxsize  gt  0x100000000   0x7fffffffffffffff   True    Python 3 6 4 x86     gt  gt  gt  import sys  gt  gt  gt   Python  0 s  on  1 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   gt  gt  gt  hex sys maxsize   sys maxsize  gt  0x100000000   0x7fffffff   False     Win 10 x64    Python 3 5 4 x64     gt  gt  gt  import sys  gt  gt  gt   Python  0 s  on  1 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   gt  gt  gt  hex sys maxsize   sys maxsize  gt  0x100000000   0x7fffffffffffffff   True    Python 3 6 2 x86     gt  gt  gt  import sys  gt  gt  gt   Python  0 s  on  1 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   gt  gt  gt  hex sys maxsize   sys maxsize  gt  0x100000000   0x7fffffff   False           Use  Python 3 Docs   struct calcsize format  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     gt  gt  gt  import struct  gt  gt  gt  struct calcsize  P     8 64    Ubuntu 16 x64    Python 3 5 2 x64     gt  gt  gt  import struct  gt  gt  gt  struct calcsize  P     8 64   Python 3 6 4 x86     gt  gt  gt  import struct  gt  gt  gt  struct calcsize  P     8 32    Win 10 x64    Python 3 5 4 x64     gt  gt  gt  import struct  gt  gt  gt  struct calcsize  P     8 64   Python 3 6 2 x86     gt  gt  gt  import struct  gt  gt  gt  struct calcsize  P     8 32          Use  Python 3 Docs   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     gt  gt  gt  import ctypes  gt  gt  gt  ctypes sizeof ctypes c void p    8 64    Ubuntu 16 x64    Python 3 5 2 x64     gt  gt  gt  import ctypes  gt  gt  gt  ctypes sizeof ctypes c void p    8 64   Python 3 6 4 x86     gt  gt  gt  import ctypes  gt  gt  gt  ctypes sizeof ctypes c void p    8 32    Win 10 x64    Python 3 5 4 x64     gt  gt  gt  import ctypes  gt  gt  gt  ctypes sizeof ctypes c void p    8 64   Python 3 6 2 x86     gt  gt  gt  import ctypes  gt  gt  gt  ctypes sizeof ctypes c void p    8 32           Python 3 Docs   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     gt  gt  gt  import platform  gt  gt  gt  platform architecture     64bit          Ubuntu 16 x64    Python 3 5 2 x64     gt  gt  gt  import platform  gt  gt  gt  platform architecture     64bit    ELF     Python 3 6 4 x86     gt  gt  gt  import platform  gt  gt  gt  platform architecture     32bit    ELF      Win 10 x64    Python 3 5 4 x64     gt  gt  gt  import platform  gt  gt  gt  platform architecture     64bit    WindowsPE     Python 3 6 2 x86     gt  gt  gt  import platform  gt  gt  gt  platform architecture     32bit    WindowsPE            Lame workaround  gainarie  - invoke an external command   man7   FILE 1   via  Python 3 Docs   os system command   The limitations of  4  apply  sometimes it might not even work     OSX 9 x64    Python 2 7 10 x64     gt  gt  gt  import os  gt  gt  gt  os system  file  0 s   format os path realpath sys executable     opt OPSWbuildtools 2 0 6 bin python2 7 global  Mach-O 64-bit executable x86 64    Ubuntu 16 x64    Python 3 5 2 x64     gt  gt  gt  import os  gt  gt  gt  os system  file  0 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     gt  gt  gt  import os  gt  gt  gt  os system  file  0 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 3rd Party tools that can be used  but I m not going to insist on them       Win specific    Check env vars  e g   PROCESSOR ARCHITECTURE   or others   via  Python 3 Docs   os environ    Win 10 x64    Python 3 5 4 x64     gt  gt  gt  import os  gt  gt  gt  os environ  PROCESSOR ARCHITECTURE    AMD64    Python 3 6 2 x86     gt  gt  gt  import os  gt  gt  gt  os environ  PROCESSOR ARCHITECTURE    x86            Python 3 Docs   sys version  also displayed in the 1st line when starting the interpreter    Check  1

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C  Users xyz gt python  Python 2 7 6  default  Nov XY      19 24 24     MSC v 1500 64 bit  AMD64   on win 32   Type  help    copyright    credits  or  license  for more information   gt  gt  gt    after hitting python in cmd

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platform architecture   is problematic  and expensive    Conveniently test for sys maxsize  gt  2  32 since Py2 6     This is a reliable test for the actual  default  pointer size and compatible at least since Py2 3  struct calcsize  P      8  Also  ctypes sizeof ctypes c void p     8    Notes  There can be builds with gcc option -mx32 or so  which are 64bit architecture applications  but use 32bit pointers as default  saving memory and speed    sys maxsize   ssize t  may not strictly represent the C pointer size  its usually 2  31 - 1 anyway   And there were are systems which have different pointer sizes for code and data and it needs to be clarified what exactly is the purpose of discerning  32bit or 64bit mode

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For 32 bit it will return 32 and for 64 bit it will return 64  import struct print struct calcsize  P     8

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Based On abe32 s answer   import sys n bits   32  lt  lt  bool sys maxsize  gt  gt  32    n bits will have 32 or 64 bits

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For a non-programmatic solution  look in the Activity Monitor  It lists the architecture of 64-bit processes as    Intel  64-bit

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On my Centos Linux system I did the following   1  Started the Python interpreter  I m using 2 6 6  2  Ran the following code   import platform print platform architecture      and it gave me    64bit   ELF

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When starting the Python interpreter in the terminal command line you may also see a line like    Python 2 7 2  default  Jun 12 2011  14 24 46   MSC v 1500 64 bit  AMD64   on win32   Where  MSC v 1500 64 bit  AMD64   means 64-bit Python  Works for my particular setup

[python] How do I determine if my python shell is executing in 32bit or 64bit?

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