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repeated-equality-comparison (PLR1714)

Added in v0.0.279 · Related issues · View source

Derived from the Pylint linter.

Fix is always available.

What it does

Checks for repeated equality comparisons that can be rewritten as a membership test.

This rule will try to determine if the values are hashable and the fix will use a set if they are. If unable to determine, the fix will use a tuple and suggest the use of a set.

Why is this bad?

To check if a variable is equal to one of many values, it is common to write a series of equality comparisons (e.g., foo == "bar" or foo == "baz").

Instead, prefer to combine the values into a collection and use the in operator to check for membership, which is more performant and succinct. If the items are hashable, use a set for efficiency; otherwise, use a tuple.

Fix safety

This rule is always unsafe since literal sets and tuples evaluate their members eagerly whereas or comparisons are short-circuited. It is therefore possible that a fix will change behavior in the presence of side-effects.

Example

foo == "bar" or foo == "baz" or foo == "qux"

Use instead:

foo in {"bar", "baz", "qux"}

References