How to auto run python jobs using crontab

In ubuntu Linux，many times we need to run certain tasks regularly, such as every 10 minutes, at 2 o’clock in the morning every day, etc.
The tasks can be varied, but as data scientists, many of our tasks are based on python code.

A simple python job

Suppose we have a very simple python text that needs to be run at 2 AM every day. The python text is named test.py, and the code is as follows:

a=3
b=5
print(a+b)

we could write a bash script，run.sh to run the above python job：

#!/bin/bash
python test.py >> log.txt

we need to make the run.sh to be excecutable:

chmod +x run.sh

We then can run the script，implement the python code，got the answer of a+b and pipeline it to the file log.txt:

./run.sh

Our job is now to figure out how to run.sh script file automatically。

Install crontab

If your ubuntu doesn’t have contab

install：apt-get install cron
start：service cron start
restart：service cron restart
stop：service cron stop
check status：service cron status
check scheduled jobs：crontab -l

add crontab job

the command is：

crontab -e

follow the hint and choose the edit environment you like, such as nano or vi.
If we want to run the job 2 am every day, the logic is like this:

0 2 * * * /home/user_name/run.sh

If we want to run the job every 5 minutes, then rule is this:

*/5 * * * * /home/user_name/run.sh

After save the above work, we have successfully scheduled the jobs.
Using the following command,

crontab -l

we could confirm all the scheduled jobs including the one we just put in.