16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
48 lines
1.4 KiB
Plaintext
48 lines
1.4 KiB
Plaintext
== Why is this an issue?
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A common anti-pattern is to check that a key does not exist in a dictionary before adding it with a corresponding value. This pattern works but is less readable than the equivalent call to the built-in dictionary method "setdefault()".
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Note that if a default value is set for every key of the dictionary it is possible to use python's ``++defaultdict++`` instead.
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This rule raises an issue when a key presence is checked before being set. It only raises an issue when the value is a hard-coded string, number, list, dictionary or tuple. Computed values will not raise an issue as they can have side-effects.
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=== Noncompliant code example
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[source,python]
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----
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if "key" not in my_dictionary:
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my_dictionary["key"] = ["a", "b", "c"] # Noncompliant
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if "key" not in my_dictionary:
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my_dictionary["key"] = generate_value() # Compliant. No issue is raised as generate_value() might have some side-effect.
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----
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=== Compliant solution
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[source,python]
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----
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my_dictionary.setdefault("key", ["a", "b", "c"])
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# OR, if ["a", "b", "c"] is the default value for every key
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from collections import defaultdict
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my_dictionary = defaultdict(lambda: ["a", "b", "c"])
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Replace this key check and dictionary update with a call to "setdefault"
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endif::env-github,rspecator-view[]
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