delete all keys except one in dictionary
Why don't you just create a new one?
lang = {'en': lang['en']}Edit: Benchmark between mine and jimifiki's solution:
$ python -m timeit "lang = {'ar':'arabic', 'ur':'urdu','en':'english'}; en_value = lang['en']; lang.clear(); lang['en'] = en_value"1000000 loops, best of 3: 0.369 usec per loop$ python -m timeit "lang = {'ar':'arabic', 'ur':'urdu','en':'english'}; lang = {'en': lang['en']}"1000000 loops, best of 3: 0.319 usec per loopEdit 2: jimifiki's pointed out in the comments that my solution keeps the original object unchanged.
Iterate over keys() instead:
for k in lang.keys(): if k != 'en': del lang_name[k]If you're using Python 3 I believe you need to use list(lang.keys()) instead.