Calculate file sizes for selected system file types

calculate_file_sizes.py

import re
from collections import OrderedDict

# re.MULTILINE
line_pattern = re.compile('^([\w\W]+)\.([\w\d]+)\s(\d+)b$')
selected_file_types = {
    'music': ['mp3', 'aac', 'flac'],
    'images' : ['jpg', 'bmp', 'gif'],
    'movies' : ['mp4', 'avi', 'mkv'],
    'other' : ['7z', 'txt', 'zip', 'exe']
}

def get_line_match(line):
    """Matching groups from `self.line_pattern`
        Group 0 - File line
        Group 1 - File name
        Group 2 - File suffix
        Group 3 - File size in bytes (b)
    """
    return line_pattern.match(line) if line_pattern.match(line) else False

def solution(S):
    lines = S.split('\n')
    results = ''
    result = "{0} {1}b\n"

    # Hard coded result keys, due to time
    calculations = {
        'music': int(0),
        'images': int(0),
        'movies': int(0),
        'other': int(0)
    }

    # Preseve output sequence, ordered by key
    ordered_calculations = OrderedDict(sorted(calculations.items(), key=lambda t: t[0]))

    # Extract input data
    for line in lines:
        file_match = get_line_match(line)
        if file_match:
            # Added for readability, and Python 3 forward compatibility
            # slower processing in python 2.7 vs a line for line generator
            for key, value in selected_file_types.items():
                # Does the suffix exist and is it sort after
                if file_match.group(2) in value:
                    if file_match.group(3) > 0:
                        ordered_calculations[key] += int(file_match.group(3))

    # Format data results
    for key, value in ordered_calculations.items():
        results += result.format(key, value)

    return results

if __name__ == '__main__':
    results = solution(
        'my.song.mp3 11b\ngreatSong.flac 1000b\nnot3.txt 5b\nvideo.mp4 200b\ngame.exe 100b\nmov!e.mkv 10000b'
    )
    print results