convert duration string like: 2d3h5m30s into seconds only (python)

duration_string_to_seconds.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import re
test_str = "1h5m"
test_str = "5d3h2m50s"

keys = {
    'd' : 60 * 60 * 24,
    'h' : 60 * 60,
    'm' : 60,
    's' : 1,
}
alphas = [i for i in re.split('[0-9]+', test_str) if i]
nums   = [i for i in re.split('[a-z]+', test_str.lower()) if i]
retval = 0
for idx, metric in enumerate(alphas):
    if metric not in keys.keys():
        raise Exception("Error, bad metric value: {}, need: {}".format(metric, keys.keys()))
    retval += int(keys[metric]) * int(nums[idx])
print(retval)