41 lines
1.3 KiB
Plaintext
41 lines
1.3 KiB
Plaintext
A common anti-pattern is to check that a key exists in a dictionary before retrieving its corresponding value and providing a default value otherwise. This pattern works but is less readable than the equivalent call to the built-in dictionary method "get()" with a default value.
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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 retrieving its value or providing a default value. It only raises an issue when the default 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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----
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result = "default"
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if "missing" in mydict:
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result = mydict["missing"] # Noncompliant
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if "missing" in mydict:
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result = mydict["missing"] # Noncompliant
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else:
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result = "default"
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if "missing" in mydict:
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result = mydict["missing"] # Compliant. No issue is raised as generate_value() might have some side-effect.
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else:
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result = generate_value()
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----
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== Compliant Solution
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----
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result = mydict.get("missing", "default")
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# OR, if "default" is the default value for every key
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from collections import defaultdict
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mydict = defaultdict(lambda: "default")
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result = mydict["missing"]
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----
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