Assign dict values to list if they exist, otherwise none

Right now, i have something like that:

media_info = MediaInfo.parse(file_path).to_data()
local_file_info = [ media_info['tracks'][1]['frame_rate'],
media_info['tracks'][1]['other_display_aspect_ratio'],
media_info['tracks'][2]['other_sampling_rate'],
media_info['tracks'][2]['other_channel_s'],
media_info['tracks'][3]['Format']]


How can i dumbproof this to assign None instead of throwing IndexError when element doesn't exist? (Example: file parsed with MediaInfo doesn't have subtitle track in video file, so there is no 3rd track)

I know i could do it the dirty way:

try:
local_file_info.append(media_info['tracks'][1]['frame_rate'])
except IndexError
local_file_info.append(None)

try:
local_file_info.append(media_info['tracks'][1]['other_display_aspect_ratio'])
except IndexError
local_file_info.append(None)

try:
local_file_info.append(media_info['tracks'][2]['other_sampling_rate'])
except IndexError
local_file_info.append(None)

try:
local_file_info.append(media_info['tracks'][2]['other_channel_s'])
except IndexError
local_file_info.append(None)

try:
local_file_info.append(media_info['tracks'][3]['Format'])
except IndexError
local_file_info.append(None)


But that just looks horrible and i'm sure there is better way to do that.

2 Answers
2

The obvious problem with your code is the massive code duplication. Two useful tools for reducing code duplication are

media_info

try...except

Ideally, you should do both:

media_keys = [
(1, 'frame_rate'),
(1, 'other_display_aspect_ratio'),
(2, 'other_samping_rate'),
(2, 'other_channel_s'),
(3, 'Format')
]

def get_media_info(index, key):
try:
return media_info['tracks'][index][key]
except IndexError:
return None

local_file_info = [get_media_info(*keys) for keys in media_keys]


a quick fix would be using if conditions

if 3 in media_info['tracks'].keys():
local_file_info.append(media_info['tracks'][3]['Format'])
else:
local_file_info.append(None)


but it still doesn't fix your problem, since it still looks horrible but atleast its not the dirty way

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