[SOLVED] python-script does not load libraries when invoked by cron

Issue

I have a python-script that uses matplotlib and pandas to load and plot some data. The python-script is not worth mentioning.

If a usual user (eg pi) starts this script, it does well. But soon as cron starts the same script, libraries such as pandas can not be loaded any more.

To gain some more information I wrapped the python-script in a bash-script. I have checked env (including PATH) and they seem to be the same for cron and pi. As long as usual user pi starts the script, it looks well:

Start plot_mean_error_by_hour.bash
SHELL=/bin/bash
LANGUAGE=de_DE.UTF-8
NO_AT_BRIDGE=1
PWD=/home/pi/public_html
LOGNAME=pi
XDG_SESSION_TYPE=tty
HOME=/home/pi
LANG=de_DE.UTF-8
LS_COLORS=rs=0: ... :*.xspf=00;36:
SSH_CONNECTION=192.168.178.20 51164 192.168.178.40 22
XDG_SESSION_CLASS=user
TERM=xterm-256color
USER=pi
DISPLAY=localhost:10.0
SHLVL=2
XDG_SESSION_ID=40005
XDG_RUNTIME_DIR=/run/user/1000
SSH_CLIENT=192.168.178.20 51164 22
LC_ALL=de_DE.UTF-8
PATH=.:/:/usr/bin/python3:/usr/lib/python3/dist-packages:/usr/lib/python3/dist-packages/pandas:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games:/home/pi/public_html:/home/pi/public_html/plot_mean_error_by_hour.bash
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
MAIL=/var/mail/pi
SSH_TTY=/dev/pts/0
OLDPWD=/home/pi
TEXTDOMAIN=Linux-PAM
_=/usr/bin/env
got pandas from ['/usr/lib/python3/dist-packages/pandas']
can read /home/pi/public_html/testprovider.hdf
read /home/pi/public_html/testprovider.hdf
...
labeled plot
wrote /home/pi/public_html/testprovider.svg

But when cron uses the same bash-script python fails loading its libraries:

Start plot_mean_error_by_hour.bash
SHELL=/bin/bash
LANGUAGE=de_DE.UTF-8
PWD=/home/pi
LOGNAME=pi
HOME=/home/pi
LANG=de_DE.UTF-8
SHLVL=1
LC_ALL=de_DE.UTF-8
PATH=.:/:/usr/bin/python3:/usr/lib/python3/dist-packages:/usr/lib/python3/dist-packages/pandas:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games:/home/pi/public_html:/home/pi/public_html/plot_mean_error_by_hour.bash
_=/usr/bin/env

Both PATH- and SHELL-variables are just the same and I like to get some more information why python launched by cron fails. How can I get more information?

Thanx for any hint

Solution

Silly me! source just did the trick. Added source /home/pi/.bashrc to the bash-script and python does load it all as supposed.

Answered By - Christian

Answer Checked By - Robin (WPSolving Admin)