[QGIS-Developer] External python package dependency in plugins

[Luke Pinner]

Rather than using a subprocess and needing to figure out which pip/python
etc., have you tried importing and using the pip module directly? Something
like:

import sys

try:
    import matplotlib
except:
    import pip    pip.main(['install', 'matplotlib'])    import matplotlib

Luke

On Sun., 8 Jul. 2018, 15:42 Axel Andersson, <axel.n.c.andersson at gmail.com>
wrote:

> Hi,
>
> I added this to my code just 3 days ago :)
>
> import sys
>
> try:
>     import matplotlib
> except:
>     import subprocess
>     print('installing matplotlib')
>     subprocess.call([sys.exec_prefix + '/python', "-m", 'pip', 'install', 'matplotlib'])
>     import matplotlib
>     print('installation completed')
>
>
> I dont know if it is a better or worse solution, I've only tested it on a
> Windows machine with the standalone version and the osgeo4w installation.
>
> I tried calling sys.executable first, instead of sys.exec_prefix +
> '/python', which resulted in a new qgis window started :)
>
> Axel
>
> On 7 July 2018 at 14:23, Richard Duivenvoorde <rdmailings at duif.net> wrote:
>
>> On 07/07/2018 01:26 PM, shiva reddy wrote:
>> > Thanks,
>> > In OS X following works:
>> > subprocess.call(['pip3','install','pyxform'])
>> >
>> > Does same works  works for Ubuntu/linux also?
>> >
>> > for windows, I am assuming 'python' refers to python 3 inside QGIS3.
>>
>> Yep:
>>
>> import subprocess
>> subprocess.call(['pip3','install','pyxform','--user'])
>>
>> works too.
>>
>> But as said, not sure if all distro's call the python3 pip: pip3 (and/or
>> python3). I still would be afraid to force a specific version of a
>> module, as I would be afraid to override some excisting one.
>> I do like your solution though, the libs end up in my user site-packages
>> dir:
>> /home/richard/.local/lib/python3.5/site-packages
>>
>>
>> Ah: http://zetcode.com/lang/python/introspection/
>> >>> import sys
>> >>> sys.executable
>> '/usr/bin/python3'
>>
>> gives you your actual python exe...
>>
>> I wonder if you can create an venv from within QGIS in the subprocess way.
>> Mmm, this works (from within QGIS):
>>
>> >>> import sys
>> >>> py_exe = sys.executable
>> >>> venv_path =
>> '/home/richard/.local/share/QGIS/QGIS3/profiles/default/venv'
>> >>> subprocess.call([py_exe,'-m','venv', venv_path])
>>
>> Had to install python3-venv though:
>> sudo apt-get install python3-venv
>>
>> sourcing it does not work with me:
>>
>> >>> subprocess.call(['source', venv_path+'/bin/activate'])
>> FileNotFoundError: [Errno 2] No such file or directory: 'source'
>>
>> Now somebody with more knowledge of the different python-path/lib-dir's
>> should come in, to tell us if this is usable after activating that venv...
>>
>> Not sure if this would work with the already running python interpreter
>> in QGIS...
>>
>> Idea's?
>>
>> Regards,
>>
>> Richard Duivenvoorde
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>
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