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bit-count (FURB161)

Added in 0.5.0 · Related issues · View source

Derived from the refurb linter.

Fix is always available.

What it does

Checks for uses of bin(...).count("1") to perform a population count.

Why is this bad?

In Python 3.10, a bit_count() method was added to the int class, which is more concise and efficient than converting to a binary representation via bin(...).

Example

x = bin(123).count("1")
y = bin(0b1111011).count("1")

Use instead:

x = (123).bit_count()
y = 0b1111011.bit_count()

Fix safety

This rule's fix is marked as unsafe unless the argument to bin can be inferred as an instance of a type that implements the __index__ and bit_count methods because this can change the exception raised at runtime for an invalid argument.

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