store return value of a Python script in a bash script

Question

I want to execute a python script from a bash script  and I want to store the output of the python script in a variable    In my python script  I print some stuff to screen and at the end I return a string with   sys exit myString     In my bash script  I did the following   outputString  python myPythonScript arg1 arg2 arg3     But then when I check the value of outputString with echo  outputString I get everything that the Python script had printed to screen  but not the return value myString   How should I do this   EDIT  I need the string because that tells me where a file created by the Python script is located  I want to do something like   fileLocation  python myPythonScript1 arg1 arg2 arg1  python myPythonScript2  fileLocation

User · Answer

sys exit   should return an integer  not a string   sys exit 1    The value 1 is in        cat e py import sys sys exit 1    python e py   echo    1   Edit   If you want to write to stderr  use sys stderr

User · Answer

Do not use sys exit like this  When called with a string argument  the exit code of your process will be 1  signaling an error condition  The string is printed to standard error to indicate what the error might be  sys exit is not to be used to provide a  return value  for your script   Instead  you should simply print the  return value  to standard output using a print statement  then call sys exit 0   and capture the output in the shell

User · Answer

Python documentation for sys exit  arg  says      The optional argument arg can be an integer giving the exit status  defaulting to zero   or another type of object  If it is an integer  zero is considered    successful termination    and any nonzero value is considered    abnormal termination    by shells and the like  Most systems require it to be in the range 0-127  and produce undefined results otherwise     Moreover to retrieve the return value of the last executed program you could use the    bash predefined variable    Anyway if you put a string as arg in sys exit   it should be printed at the end of your program output in a separate line  so that you can retrieve it just with a little bit of parsing  As an example consider this   outputString  python myPythonScript arg1 arg2 arg3   tail -0

User · Answer

sys exit myString  doesn t mean  return this string   If you pass a string to sys exit  sys exit will consider that string to be an error message  and it will write that string to stderr  The closest concept to a return value for an entire program is its exit status  which must be an integer   If you want to capture output written to stderr  you can do something like   python yourscript 2 gt  return file   You could do something like that in your bash script  output    your command here  2 gt   amp 1    This is not guaranteed to capture only the value passed to sys exit  though  Anything else written to stderr will also be captured  which might include logging output or stack traces   example   test py  print  something  exit  ohoh      t sh  va   python test py 2 gt  amp 1                                                                                                                      mkdir  va   bash t sh  edit  Not sure why but in that case  I would write a main script and two other scripts    Mixing python and bash is pointless unless you really need to   import script1 import script2  if   name         main         filename   script1 run sys args      script2 run filename

User · Answer

In addition to what Tichodroma said  you might end up using this syntax   outputString   python myPythonScript arg1 arg2 arg3

User · Answer

read it in the docs  If you return anything but an int or None it will be printed to stderr     To get just stderr while discarding stdout do   output   python foo py 2 gt  amp 1  gt  dev null

[python] store return value of a Python script in a bash script

Examples related to python

Examples related to bash

Examples related to return

Examples related to return-value