subprocess problem

[Andreas Paeffgen]

The Problem with the subprocess code is: Using the sourcecode 
functioning as normal.

The frozen app with cx_freeze on every platform just returns an empty result

Here is the code in short:
def get_path_pandoc():




   settings = QSettings('Pandoc', 'PanConvert')

   path_pandoc = settings.value('path_pandoc','')




   if not os.path.isfile(path_pandoc):




   if platform.system() == 'Darwin' or os.name == 'posix':

   args = ['which', 'pandoc']

   p = subprocess.Popen(

   args,

   stdin=subprocess.PIPE,

   stdout=subprocess.PIPE)




   path_pandoc = 
str.rstrip(p.communicate(path_pandoc.encode('utf-8'))[0].decode('utf-8')) 




The whole problematic code can be checked on 
http://github.com/apaeffgen/panconvert

in source/converters/interface_pandoc.py

I debugged it with some QMessage-Boxes. I just know, that the returnd 
result is empty.

I tried some stderr on this code also. But also the error message is empty.

Any hints what could be changed in the code, so it also works in the 
frozen app?


At the moment i use python3.4 to 3.5 depending on the platform (Mac, 
Win, Linux)


P.S. Tried also some code with invoking the bash and afterwords the 
which pandoc code. To know avail also




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Re: subprocess problem

[Andreas Paeffgen]

Maybe i could use another trick to circumvent the problems in the 
frozen app? The frozen apps can be downloaded here: 
https://sourceforge.net/projects/panconvert/files/Newest/


@Cameron:

1. I use PyQT5 for a creating a gui app. To run the app on other 
systems, where no QT5 and PyQT5 is installed, a bundle is created with 
all relevant libraries, so it will start independently. This app 
bundle, is called a frozen app. Not only the source code, but all it 
dependencies are distributed including python3 itself.


2. In the test-environment pandoc is installed in /usr/local/bin/pandoc 
(Mac) or /bin/pandoc (Linux). Which returns the path correctly, at the 
terminal (shell), in Python and in the Gui-App Panconvert.


3. I am aware of the limitations of which. There is a fallback to 
manually insert the path. So the app will function anyway.  And i want 
to avoid to search the whole filesystem. This takes minutes on my test 
machines, so this is no option.


4. I suppose that something is different from executing the code in the 
frozen state. The app e.g. on Mac is not started from a python shell or 
a comand shell. But even on linux, when started from a shell it does 
not work.


5. I will try the hint with dev.null and the p.check_returncode()



@Wolfgang

1. The function should be executed only, if the path is unknown. If the 
user enters the path manually in the settings and pandoc exists, the 
function should not be executed to save computation time.


2. Only if the manually entered path is not correct or empty the 
function should be executed,  hence 'if not os.path.isfile(path_pandoc)'


3. The function fills in the path automatically if which returns a 
value. This works in the source code



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Re: subprocess problem

[Andreas Paeffgen]

I guess which does not return an error code. If it does not find 
anything, the return is just blank. If it finds something, the path is 
returned.


So the change of code did not help, because there is just no error message.
Could there be a $path problem in the subprocess started inside the binary?


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Re: subprocess problem

[Andreas Paeffgen]

Thanks for all the great advice.
I tested all the possibilities. So far no luck. If i start the app from 
a terminal, the solutions work. But not, if i start the app-bundle 
(There is no connection to a terminal)


1. Copied the path to p.subprocess
2. Used the def wich: python function
3. Used shutil

When there is no Terminal, there is no error message / status code message.


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Re: subprocess problem

[Andreas Paeffgen]

On 2017-02-11 02:23:12 +, Cameron Simpson said:


  def your_function(...):
with open('/path/to/your/logfile.txt', 'a') as logfp:
  print("PATH=".os.environ['PATH'], file=logfp)
  p=Popen(...)
  p.communicate(...)
  print("p.returncode=%r" % (p.returncode))

and any other interesting values that occur to you. This is really simple, and
doesn't require a terminal or using the logging module.

You can 'tail -f /path/to/your/logfile.txt' in another terminal to watch stuff
happen as you exercise the program.


Thanks for the great advice.
I found out, that the frozen app does not pass the normal path 
variable. All the tricks with passing the correct environment did not 
work. I just hardcoded the existing standard path. After that it worked.


I think it is a problem with frozen apps in general. Cx_Freeze has 
other problems than Pyinstaller. But all need some workarounds for the 
problems.




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