Python existing scripts to call

I have got quite a lot Python scripts running om my Pi’s. Most of them stores data in MySQL. Now i like to retrieve some data and show them on the dashboard.
Mostly humidity and temperature data.

The Python script i use puts everything in a list [date, time, var1 …var10]
and create excel data to produce graphs.

Now i am using HomeAssistance and want to usu this platform to show data like MaxCube is doing.

Question:
Can I use these retrieve Python scrips, which must be modified for version 3.5
( currently version 2.7) and add the HomeAssistant hass calls. Or are there other methods to retrieve data from MySQL?

How do i call python scrips to run in HomeAssistance? I did not find any clear explanation what to do the configuration.yaml and how to call a service.

Is there a timer which i can use to call python scrips or do i to program it in the python script.?

I like the idea to modify existing push scripts, just to avoid a lot of work to write, test new ones.

Existing architecture and background info:

Collect data ==> push data to ==>SqlServer

Pi Zero No1 ---------------
|
Pi Zero No2 --------------- --------- Pi3B SqlLite Server
| |
Pi Zero No3 -------------- |
|
Pi3B Test
extracting data

every 5 minutes data ts pushed to the SQL server, Every script is synchronised by a timer script so that data is collected at the same time but not pushed at the same time.

Pi3B for HomeAssistant

I use Notepad++ to develop scripts
SqlWorkbench to develop and test SQL queries
VNC to connect to the different Pi’s and move the scripts to them.