This rule raises an issue when trying to access a dictionary key that does not exist.

== Why is this an issue?

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

[source,python,diff-id=1,diff-type=noncompliant]
----
def foo():
    my_dict = {'k1': 42}
    ...
    value = my_dict['k2']  # Noncompliant: the key "k2" does not exist.
----

==== Compliant solution

[source,python,diff-id=1,diff-type=compliant]
----
def foo():
    my_dict = {'k1': 42}
    ...
    if 'k2' in my_dict:
        value = my_dict['k2']
----

== Resources 

=== Documentation

* Python Documentation - https://docs.python.org/3/library/stdtypes.html?highlight=setdefault#dict.setdefault[dict - setdefault]
* Python Documentation - https://docs.python.org/3/library/collections.html#collections.defaultdict[defaultdict]
* Python Documentation - https://docs.python.org/3/library/collections.html?highlight=default_factory#collections.defaultdict.default_factory[defaultdict - default_factory]


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Fix this access on a dictionary key that may be missing.
Fix this "pop" operation on a dictionary key that may be missing.
Fix this "del" operation on a dictionary key that may be missing.


'''
endif::env-github,rspecator-view[]
