unnecessary-key-check (RUF019)

Fix is always available.

This rule is unstable and in preview. The --preview flag is required for use.

What it does

Checks for unnecessary key checks prior to accessing a dictionary.

Why is this bad?

When working with dictionaries, the get can be used to access a value without having to check if the dictionary contains the relevant key, returning None if the key is not present.

Examples

if "key" in dct and dct["key"]:
    ...

Use instead:

if dct.get("key"):
    ...