Python 3.5 version

ext_info.py

import collections
import pathlib
import sys


USAGE = """usage: {} path
displays number of files and total size per extension in the specified path."""


def get_info(path):
    info = collections.defaultdict(lambda: {'count': 0, 'size': 0})

    folder = pathlib.Path(path)
    for f in folder.iterdir():
        if not f.is_file():
            continue
        ext = f.suffix[1:] or '.'
        info[ext]['count'] += 1
        info[ext]['size'] += f.stat().st_size

    return info


# print(get_info('.'))
# print(get_info('/usr/bin').items())
# print(get_info('/usr/share/pixmaps/').items())

if __name__ == "__main__":
    if len(sys.argv) != 2:
        print(USAGE.format(sys.argv[0]))
        sys.exit(1)

    info = get_info(sys.argv[1])
    for ext, d in sorted(info.items()):
        print(ext, d['count'], d['size'])