How to deal with negative numbers that returncode

Question

This piece of script in python:

cmd = 'installer.exe --install ...' #this works fine, the ... just represent many arguments
process = subprocess.Popen(cmd)
process.wait()
print(process.returncode)

This code works fine in my opinion, the problem is the value of .returncode.

The installer.exe is ok, did many test to this, and now i trying to create a script in python to automate a test for many days executing this installer.exe .

The installer.exe return: - Success is 0; - Failure and errors are NEGATIVE numbers

I have a specific error that is -307 that installer.exe return. But python when execute print(process.returncode) its shows 4294966989 ... How can i deal with negative numbers in python, to show in this case the -307?

I am new to python and the env is win7 32 and python 3.4.

EDIT: the final code working The porpose of this code is to run many simple test:

import subprocess, ctypes, datetime, time
nIndex = 0
while 1==1:

   cmd = 'installer.exe --reinstall -n "THING NAME"'
   process = subprocess.Popen( cmd, stdout=subprocess.PIPE )

   now = datetime.datetime.now()
   ret = ctypes.c_int32( process.wait() ).value
   nIndex = nIndex + 1

   output = str( now ) + ' - ' + str( nIndex ) + ' - ' + 'Ret: ' + str( ret ) + '\n'

   f = open( 'test_result.txt', 'a+' )
   f.write( output )
   f.closed

   print( output )

Answer 1

To convert positive 32-bit integer to its two's complement negative value:

>>> 4294966989 - (1 << 32) # mod 2**32
-307

As @Harry Johnston said, Windows API functions such as GetExitCodeProcess() use unsigned 32-bit integers e.g., DWORD, UINT. But errorlevel in cmd.exe is 32-bit signed integer and therefore some exit codes (> 0x80000000) may be shown as negative numbers.

Answer 2

Using only the standard library:

>>> import struct
>>> struct.unpack('i', struct.pack('I', 4294966989))
(-307,)

Answer 3

Using NumPy: view the unsigned 32-bit int, 4294966989, as a signed 32-bit int:

In [39]: np.uint32(4294966989).view('int32')
Out[39]: -307