Python plugin sys.path uses full path in base 20

snapcraft
#1

using base: core18 the sys.path uses : $SNAP/ for example:

 >>> import sys
 >>> print('\n'.join(sys.path))
 
 /snap/ubu18/x1/usr/lib/python36.zip
 /snap/ubu18/x1/usr/lib/python3.6
 /snap/ubu18/x1/usr/lib/python3.6/lib-dynload
 /snap/ubu18/x1/usr/lib/python3/dist-packages
 /snap/ubu18/x1/lib/python3.6/site-packages

using base: core20 the sys.path uses full path:

 >>> import sys
 >>> print('\n'.join(sys.path))
 
 /usr/lib/python38.zip
 /usr/lib/python3.8
 /usr/lib/python3.8/lib-dynload
 /usr/lib/python3/dist-packages
 /lib/python3.8/site-packages

is it a bug?
is there a good aproach to “fix” the path in core base 20?

#2

I only found one way to do that.
I needed to create a shell script that set environment variables:

start.sh:

PYTHONPATH="$SNAP/usr/lib/python38.zip:$SNAP/usr/lib/python3.8:$SNAP/usr/lib/python3.8/lib-dynload:$SNAP/usr/lib/python3/dist-packages:$SNAP/lib/python3.8/site-packages" python3 $SNAP/bin/ubu20.py

snapcraft.yaml:

    command: start.sh

override-stage didn’t work, setting environment variables here, doesn’t affect when running the app.

#3

Rather than setting the env variable as part of the command itself, you should be able to achieve the same runtime setting with:

environment:
  PYTHONPATH: <path>

or

apps:
  <app name>:
    environment:
      PYTHONPATH: <path>

Regarding the path discrepancy between 18 and 20, I have no idea if it’s a bug. Can you post more of your snapcraft.yaml for us to see?

#4

hi @goodsoftworx thanks. I built two very simple projects only to test.

snapcraft.yaml for core18:

name: ubu18
base: core18
version: '1'
summary: 79 char long summary
description: |
  This is my-snap's description.

grade: devel
confinement: devmode

apps:

  ubu18:
    command: bin/ubu18.py
    plugs:
    - home
    - x11
    - desktop
    - wayland

parts:

  ubu18:
    plugin: python
    source: .
    stage-packages:
      - python3-tk
      - tk-dev
      - python-tk
    requirements: ['./requirements.txt']

  dump-files:
    plugin: dump
    source: .
    organize:
      ubu18.py: bin/

snapcraft.yaml for core20

name: ubu20
base: core20
version: '1'
summary: 79 char long summary
description: |
  This is my-snap's description.

grade: devel
confinement: devmode

apps:

  ubu20:
    command: bin/ubu20.py
    plugs:
    - pulseaudio
    - home
    - audio-playback
    - x11
    - desktop
    - wayland

parts:

  ubu20:
    plugin: python
    source: .
    stage-packages:
      - python3.8-tk
      - tk-dev
      - python-tk
    python-packages:
      - tk-tools
      - customtkinter

  dump-files:
    plugin: dump
    source: .
    organize:
      ubu20.py: bin/