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

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北恋 2020-11-22 04:25

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.<

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时光说笑 (楼主)

2020-11-22 04:31

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:

>>> import sys
>>> "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'
>>> hex(sys.maxsize), sys.maxsize > 0x100000000
('0x7fffffffffffffff', True)

Ubuntu 16 x64:

Python 3.5.2 x64:

>>> import sys
>>> "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'
>>> hex(sys.maxsize), sys.maxsize > 0x100000000
('0x7fffffffffffffff', True)

Python 3.6.4 x86:

>>> import sys
>>> "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'
>>> hex(sys.maxsize), sys.maxsize > 0x100000000
('0x7fffffff', False)

Win 10 x64:

Python 3.5.4 x64:

>>> import sys
>>> "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'
>>> hex(sys.maxsize), sys.maxsize > 0x100000000
('0x7fffffffffffffff', True)

Python 3.6.2 x86:

>>> import sys
>>> "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'
>>> hex(sys.maxsize), sys.maxsize > 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:
```
>>> import struct
>>> struct.calcsize("P") * 8
64
```
- Ubuntu 16 x64:
  - Python 3.5.2 x64:
```
>>> import struct
>>> struct.calcsize("P") * 8
64
```
  - Python 3.6.4 x86:
```
>>> import struct
>>> struct.calcsize("P") * 8
32
```
- Win 10 x64:
  - Python 3.5.4 x64:
```
>>> import struct
>>> struct.calcsize("P") * 8
64
```
  - Python 3.6.2 x86:
```
>>> import struct
>>> 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:
```
>>> import ctypes
>>> ctypes.sizeof(ctypes.c_void_p) * 8
64
```
- Ubuntu 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
```

[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:

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

Ubuntu 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')

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:

>>> import os
>>> 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:

>>> import os
>>> 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:

>>> import os
>>> 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 3^rd 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:
```
>>> import os
>>> os.environ["PROCESSOR_ARCHITECTURE"]
'AMD64'
```
  - Python 3.6.2 x86:
```
>>> import os
>>> os.environ["PROCESSOR_ARCHITECTURE"]
'x86'
```

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

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