[Tutor] Open a libreoffice calc file in Python

boB Stepp robertvstepp at gmail.com
Thu Dec 22 11:20:31 EST 2016

On Wed, Dec 21, 2016 at 10:50 PM,  <cs at zip.com.au> wrote:

> To my mind the more important thing is to use the "shell=False" version of
> Popen. os.system() inherently accepts a shell command string, which means
> you need to hand quote the /home/path/to/myfile.ods. But it is better to
> pass an array of strings:
>  ['libreoffice', '--calc', path_value]
> where path_value is a Python variable containing "/home/path/to/myfile.ods"
> or whatever the path is. This way you don't need to do anything special for,
> um, "unusual" paths because you're not passing the string _through_ the
> shell.

Both you and Eryk seem to be speaking in terms of using
subprocess.Popen() directly.  So I think I need some clarification.
At https://docs.python.org/3/library/subprocess.html#using-the-subprocess-module
it says:

"The recommended approach to invoking subprocesses is to use the run()
function for all use cases it can handle. For more advanced use cases,
the underlying Popen interface can be used directly.

"The run() function was added in Python 3.5; if you need to retain
compatibility with older versions, see the Older high-level API

The OP is using Python 3.4, so that is why I referred him to the
"Older high-level API section".  Anyway this portion of the docs
suggests normally using subprocess.run().  OTOH, for using
subprocess.Popen() directly at
https://docs.python.org/3/library/subprocess.html#popen-constructor it

"The underlying process creation and management in this module is
handled by the Popen class. It offers a lot of flexibility so that
developers are able to handle the less common cases not covered by the
convenience functions."

My current understanding as to why the subprocess module is preferred
to using the older os.system() is to avoid shell injection attacks.
So my assumption is that even when using "shell=True" with either
run() or Popen(), this is avoided.  Is this true?  So on to the
requested clarification:  Are there subtleties as to when to use run()
and when to use Popen()?



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