Sum of `du -sh` sizes

sum.py

"""
du -sh * | python3 sum.py
"""

import sys
import re

numpat = re.compile("(^[0-9.]+)([a-zA-Z]*)")
total = 0.0

for line in sys.stdin:
    tokens = line.strip().split()
    if tokens:
        m = re.match(numpat, tokens[0])
        if not m:
            print(f"-- Skipped {tokens}")
            continue

        val = float(m.group(1))
        fac = m.group(2).lower()
        if fac == "":
            fac = 1
        elif fac == "k":
            fac = 1024
        elif fac == "m":
            fac = 1024**2
        elif fac == "g":
            fac = 1024**3

        total += fac*val

if total < 1024:
    print(f"-> {total}")
elif total < 1024 ** 2:
    print(f"-> {total/1024:.3f} K")
elif total < 1024 ** 3:
    print(f"-> {total/(1024**2):.3f} M")
else:
    print(f"-> {total/(1024**3):.3f} G")