Writing a script

I need to update the python runtimes from 3.6 to 3.8 for all the lambda functions in my aws account for all the regions. I need someone to write a code to automate this otherwise I am having to do manually which is very time consuming. Approach could be like List functions >select based on criteria (runtime) > append the function arn to an array > call a function to iterate through the array elements changing runtime