subprocess terminating a PowerShell Script before completion

Question

Only in Python 3.7 using subprocessing methods run , Popen etc. or even using os.system() The PowerShell Script I'm calling seems to terminate before completion. I have a much more complex script, but I have been able to simplify both the Python script and PowerShell script to exhibit the issue. The PowerShell Script is also shown below.

Here is the Python code:

''' subprocess truncates output '''

import subprocess       # subprocess library

p = subprocess.run("powershell -ExecutionPolicy ByPass -File C:/PS/testAquire.ps1",
                   shell=True, check=True, stdout=subprocess.PIPE)
print("stdout:", p.stdout)
print("stderr:", p.stderr)

This is the Python script output showing no errors:

stdout: b''
stderr: None

This is the entire contents of the result.txt file after execution using the Python script above.

Directory: C:\windows\system32\drivers


Mode                LastWriteTime         Length Name

----                -------------         ------ ----                                                                   d-----        4/12/2018   5:15 AM                en-US
d-----        4/12/2018   5:15 AM                UMDF

-a----        1/19/2017   5:43 AM           3301 1028_Dell_INS_24-7459.mrk
-a----        4/11/2018   7:34 PM          29696 afunix.sys
-a----        4/11/2018   7:34 PM        3440660 gm.dls
-a----        4/11/2018   7:34 PM            646 gmreadme.txt
-a----        9/12/2015   4:59 AM          18720 IntelMEFWVer.dll

This is the PowerShell Script

<#
.synopsis
Sample script to demonstrate unusual results when called from Python 3.7
#>

Get-ChildItem c:/windows/system32/drivers/ |  Format-Table | Out-File c:/PS/result.txt -Encoding ascii

This is the normal output of the script when run from the PowerShell Command or when using Python 2.7 to launch the PowerShell script.

Directory: C:\windows\system32\drivers


Mode                LastWriteTime         Length Name

----                -------------         ------ ----                                                                         d-----        4/11/2018   7:38 PM                DriverData
d-----        8/15/2018   5:33 PM                en-US
d-----        5/30/2018   9:31 AM                etc
d-----       11/14/2018   5:32 PM                UMDF
d-----       12/10/2018   5:50 PM                wd

-a----        1/19/2017   5:43 AM           3301 1028_Dell_INS_24-7459.mrk

-a----        4/11/2018   7:33 PM         237568 1394ohci.sys
-a----        4/11/2018   7:33 PM         107416 3ware.sys
-a----        4/11/2018   7:33 PM         654232 acpi.sys
-a----        4/11/2018   7:33 PM          20480 AcpiDev.sys
-a----        4/11/2018   7:33 PM         127904 acpiex.sys
-a----        4/11/2018   7:33 PM          12800 acpipagr.sys
-a----        4/11/2018   7:33 PM          14848 acpipmi.sys
-a----        4/11/2018   7:33 PM          13824 acpitime.sys
-a----        4/11/2018   7:33 PM        1135520 adp80xx.sys
-a----        4/11/2018   7:34 PM         626592 afd.sys
-a----        4/11/2018   7:34 PM          39424 afunix.sys
-a----        4/11/2018   7:34 PM         108032 agilevpn.sys
-a----        4/11/2018   7:34 PM         254464 ahcache.sys
-a----        9/24/2015   5:17 AM         109200 aksdf.sys
-a----        9/24/2015   5:17 AM         205528 aksfridge.sys
-a----        4/11/2018   7:33 PM         181760 amdk8.sys

... ... I reduced the output for brevity ...

-a----        4/11/2018   7:34 PM          33184 WppRecorder.sys
-a----        4/11/2018   7:34 PM          23040 ws2ifsl.sys
-a----        4/11/2018   7:33 PM          23040 WSDPrint.sys
-a----        4/11/2018   7:33 PM          25088 WSDScan.sys
-a----        4/11/2018   7:34 PM         125440 WUDFPf.sys
-a----        4/11/2018   7:34 PM         264192 WUDFRd.sys
-a----        6/15/2018  12:44 AM         295424 xboxgip.sys
-a----        4/11/2018   7:33 PM          46592 xinputhid.sys

I should note I have tried dozens of methods to launch the script with the same results.

Answer 1

Did you try to run the subprocess without using a shell? Like so:

subprocess.run(
  ["powershell", "-ExecutionPolicy", "ByPass", "-File", "C:/PS/testAquire.ps1"],
  shell=False,
)

Alternatively, if you prefer to make use of the PowerShell, why not use it to redirect the output into the destination file (simple add a redirection to the end of the command; ... > c:/output.file )

Answer 2

Thanks for looking into this. I uninstalled Python 3.7.2 and then installed 3.6.8 and it works as designed. I have not determined if the problem was 3.7.2 or something to do with the installation. I will investigate.

Again, thanks for all your help and suggestions.