Get failed keys in Try , except python 2 and 3

failed_keys_try_except.py

# We want to get the keys which failed this could be applied to other situations
# Python 3
dict_of_elements = {1: 'john', 2: 'peter', 3: 'luke', 4: 'mark'}  # can equally be a list?
failed_keys = set()
for list in dict_of_elements:
    try:
        dict_of_elements[9]  # trying to access keys that don't exist
    except Exception as e:
        f_k = e.args[0]
        failed_keys.add(f_k)

print (failed_keys) # # {9} because key 9 does not exist in the dictionary


# Python 2 would be something like this
dict_of_elements = {1: 'john', 2: 'peter', 3: 'luke', 4: 'mark'}  # can equally be a list?
failed_keys = set()
for list in dict_of_elements:
    try:
        dict_of_elements[9]  # trying to access keys that don't exist
    except KeyError, e:
        f_k = e.args[0]
        failed_keys.add(f_k)

print (failed_keys) # {9} because key 9 does not exist in the dictionary