Prometheus alert unit testing expanding notation calculator

exp_not_calculator.py

'''
Provide a Prometheus series value expanding notation expression such as: 
  - 10+0x10
  - 1+10x5
  - 100-10*10
  - 5+5x5 40+10x5
  
And get a reply:
  - 10 10 10 10 10 10 10 10 10 10 10
  - 1 11 21 31 41 51
  - 100 90 80 70 60 50 40 30 20 10 0
  - 5 10 15 20 25 30 40 50 60 70 80 90
'''
import re 

expanded = []
expanded_str = ""

print('Enter expanding notation formula:')
exp_not = input()
exp_not_splitted = exp_not.split(' ')

for formula in range(len(exp_not_splitted)):
    
    match = re.search("(?P<start_int>.*)(?P<operator>\+|-)(?P<step>.*)x(?P<times>.*)", exp_not_splitted[formula])
    
    start_int = int(match.group("start_int"))
    step = int(match.group("step"))
    times = int(match.group("times"))
    operator = match.group("operator")
    
    if operator == "+":
        expanded.append(f"{str(start_int)} ")
        for i in range(times):
            start_int = start_int + step
            expanded.append(f"{str(start_int)} ")
    if operator == "-":
        expanded.append(f"{str(start_int)} ")
        for i in range(times):
            start_int = start_int - step
            expanded.append(f"{str(start_int)} ")
            
print(f"{expanded_str.join(expanded)}")