Python sys.executable为空

Question

I am testing out doing some shenanigans with os.execve and virtual environments. I am running into the problem where sys.executable is empty if I replace the current python process with another python subprocess.

The example below shows what's going on (run this inside a python shell):

import os, sys
print(sys.executable) # works this time
os.execve("/usr/bin/python", [], {}) # drops me into a new python shell
import sys # yes, again
print(sys.executable) # is empty

The full output of me running the commands above in a python shell:

 lptp [ tmp ]: python
Python 2.7.10 (default, Oct 14 2015, 16:09:02) 
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os, sys
>>> print(sys.executable) # works this time
/usr/bin/python
>>> os.execve("/usr/bin/python", [], {}) # drops me into a new python shell
Python 2.7.10 (default, Oct 14 2015, 16:09:02) 
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys # yes, again
>>> print(sys.executable) # is empty

>>>

sys.executable being empty is causing me problems, most notably that platform.libc_ver() fails because sys.executable is empty:

>>> import platform
>>> platform.libc_ver()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/platform.py", line 163, in libc_ver
    f = open(executable,'rb')
IOError: [Errno 21] Is a directory: '/tmp'

Note that the example above was run after calling os.execve(...)

Answer 1

Python relies on argv[0] and several environment variables to determine sys.executable . When you pass an empty argv and environment, Python doesn't know how to determine its path. At the very least, you should provide argv[0] :

os.execve('/usr/bin/python', ['/usr/bin/python'], {})