Trying to access a dictionary key that does not exist will raise a KeyError exception.
When trying to access or remove a key that may not be there, several solutions are possible:
- Use the
get() method instead of a subscription. It will return None for a missing key instead of raising a
KeyError.
- Use the
setdefault() method to provide keys that may be missing with a default value.
- Check that the key is present in the dictionary with the
if key in dict: construct.
- Use a
try/except block and handle the potential KeyError exception.
- Use a
defaultdict instead of a regular dict object, and provide a default_factory attribute.
Code examples
Noncompliant code example
def foo():
my_dict = {'k1': 42}
...
value = my_dict['k2'] # Noncompliant: the key "k2" does not exist.
Compliant solution
def foo():
my_dict = {'k1': 42}
...
if 'k2' in my_dict:
value = my_dict['k2']
