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 loop

Edit 2: jimifiki's pointed out in the comments that my solution keeps the original object unchanged.

You're looking for the intersection between the set of keys in the dict and the set of values in the list. i.e. all keys that exist in both sets.

Try this:

from collections import MutableMapping


d = { 'A': 1, 'B': 2, 'C': 3, 'D': 4 }
list_of_keys_to_keep = ['B', 'C', 'F']

def remove_fields(d, list_of_keys_to_keep):
    return {key: value for key, value in d.items() if key in list_of_keys_to_keep}

print(remove_fields(d, list_of_keys_to_keep)) # -> {'B': 2, 'C': 3}

Edit: Updated name of list_of_keys_to_remove to list_of_keys_to_keep since this seems to be what it actually represents.

Edit2: Updated after Askers update. The following works for the sample provided:

from collections import MutableMapping

d = {
  'G_1': [
    {
      'ACCOUNTING_RULE_ID': '1',
      'PAYMENT_TERM_ID': '4',
      'RENEWAL_TYPE': 'RENEW'
    },
    {
      'ACCOUNTING_RULE_ID': '2',
      'PAYMENT_TERM_ID': '4',
      'RENEWAL_TYPE': 'RENEW'
    },
    {
      'ACCOUNTING_RULE_ID': '3',
      'PAYMENT_TERM_ID': '4',
      'RENEWAL_TYPE': 'DO_NOT_RENEW'
    },
    {
     'ACCOUNTING_RULE_ID': '4',
      'PAYMENT_TERM_ID': '4',
      'RENEWAL_TYPE': 'RENEW'
    }
  ]
}
list_of_keys_to_keep = ['RENEWAL_TYPE']

def filter_dict(di, keys):
    if not isinstance(di, (dict, list)):
        return di
    if isinstance(di, list):
        return [filter_dict(value, keys) for value in di]
    return {key: filter_dict(value, keys) for key, value in di.items() if key in keys or isinstance(value, (dict, list))}

print(filter_dict(d, list_of_keys_to_keep))

Output:

{'G_1': [{'RENEWAL_TYPE': 'RENEW'}, {'RENEWAL_TYPE': 'RENEW'}, {'RENEWAL_TYPE': 'DO_NOT_RENEW'}, {'RENEWAL_TYPE': 'RENEW'}]}

Using dict.pop:

d = {'some': 'data'}
entries_to_remove = ('any', 'iterable')
for k in entries_to_remove:
    d.pop(k, None)

for key, value in your_dict.items():
    if key not in your_blacklisted_set:
        print value

the beauty is that this pseudocode example is valid python code.

it can also be expressed as a list comprehension:

resultset = [value for key, value in your_dict.items() if key not in your_blacklisted_set]