calling python scripts as a sub-process

Catherine Moroney Catherine.M.Moroney at jpl.nasa.gov
Wed Nov 19 20:38:32 CET 2008


Dan Upton wrote:
> On Wed, Nov 19, 2008 at 2:13 PM, Philip Semanchuk <philip at semanchuk.com> wrote:
>> On Nov 19, 2008, at 2:03 PM, Catherine Moroney wrote:
>>
>>> The command (stored as an array of strings) that I'm executing is:
>>>
>>> ['python ../src_python/Match1.py ',
>>> '--file_ref=MISR_AM1_GRP_ELLIPSOID_GM_P228_O003571_BF_F03_0024.hdf ',
>>> '--file_cmp=MISR_AM1_GRP_ELLIPSOID_GM_P228_O003571_DF_F03_0024.hdf ',
>>> '--block_start=62 ', '--block_end=62 ', '--istep=16 ', "--chmetric='M2' ",
>>> "--use_textid='true '"]
>>>
>> [snip]
>>
>>> I get the error below.  Does anybody know what this error refers
>>> to and what I'm doing wrong?  Is it even allowable to call another
>>> script as a sub-process rather than calling it directly?
>>>
>>> File "../src_python/Match4.py", line 24, in RunMatch4
>>>   sub1 = subprocess.Popen(command1)
>>>  File "/usr/lib64/python2.5/subprocess.py", line 593, in __init__
>>>   errread, errwrite)
>>>  File "/usr/lib64/python2.5/subprocess.py", line 1051, in _execute_child
>>>   raise child_exception
>>> OSError: [Errno 2] No such file or directory
>> Try supplying a fully-qualified path to your script, e.g.:
>> ['python /home/catherine/src_python/Match1.py ',
>> '--file_ref=MISR_AM1_GRP_ELLIPSOID_GM_P228_O003571_BF_F03_0024.hdf ',
>> '--file_cmp=MISR_AM1_GRP_ELLIPSOID_GM_P228_O003571_DF_F03_0024.hdf ',
>> '--block_start=62 ', '--block_end=62 ', '--istep=16 ', "--chmetric='M2' ",
>> "--use_textid='true '"]
> 
> I think when I came across this error, I added shell=True, e.g.
> 
> sub1 = subprocess.Popen(command, shell=True)

I added the shell=True and this time it got into Match1 (hurrah!),
but it then opened up an interactive python session, and didn't
complete until I manually typed 'exit' in the interactive session.

Match1 looks like:

if __name__ == "__main__":
<<< parse arguments >>>

     RunMatch1(file_ref, file_cmp, iblock_start, iblock_end, \
               nlinep, nsmpp, mindispx, maxdispx, mindispl,  \
               maxdispl, istep, chmetric, use_textid)

     exit()

where the routine RunMatch1 does all the actual processing.

How do I get Match1 to run and exit normally without opening up an
interactive session, when called as a subprocess from Match4?

Catherine



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