Is it safe to use the variable from dictionary comprehension during error handling?

Consider the following example:

config_parameters = ['PARAM1', 'PARAM2', 'PARAM3']
sample_config = {
    'PARAM1': 'Value1',
    'PARAM2': 'Value2'
}

try:
    # Collects param values from the sample config
    config = {k: sample_config[k] for k in config_parameters}
except KeyError as e:
    # Tries using comprehension var `k` to advise which variable was missing
    raise KeyError(f'Value: "{k}" missing from config file.')

In error handling, it tries to catch key errors that arise during a strict dict lookup step which using dict comprehension. For any caught errors, it attempts to utilize a variable that was assigned during the dict comprehension.

Is this considered safe with Python, or is there any reason to expect that k may not indicate the same value which caused the error?

>Solution :

Variables defined in a comprehension are considered local to the comprehension, so k cannot be used outside of the dict display. (This was a change made in Python 3 to prevent such leakage.)

Assignment expressions were specifically defined to allow the "extraction" of a value from that anonymous namespace, however. (See https://peps.python.org/pep-0572/#scope-of-the-target)

try:
    # Collects param values from env vars
    config = {k: sample_config[(offending_key := k)] for k in config_parameters}
except KeyError:
    raise KeyError(f'Value: "{offending_key}" missing from config file.')

k is local to the comprehension; offending_key is local to whatever scope contains the comprehension.