How to Connect Web Service Task to Python Code?

Unless you use the Qualtrics API, there's no option to send data in a CSV format, that transformation will have to be done by you. I think the API doesn't work at individual response level, but can be automated per a schedule.
In terms of getting the data, one option would be setup and action to send an email, you can extract the relevant data from there. Alternatively, you could setup a POST request right at the end of your survey, which sends the relevant data to your endpoint, which can then processed by your python code.
The first option requires less time spent within Qualtrics but you'll spend time making python parse the email. The later option is more tedious, as you'll have to select each field individually, capture randomization order on your own etc. However, you'll get clean data for python.