main.py

#!/usr/bin/env python3
from myfunctions import f1, f2, f3

for func in [f1, f2, f3]:
    func()

myfunctions.py

#!/usr/bin/env python3
def f1():
    print("I am the first function!") 

def f2():
    print("I am the second function!") 

def f3():
    print("I am the third function!") 

runner.sh

#!/bin/sh
python main.py