pylint-dev/pylint

Expand to ``use-implicit-booleaness-not-len`` to catch `len(iterable) == 0` and `>0`

Open

#10,281 创建于 2025年3月17日

在 GitHub 查看
 (24 评论) (0 反应) (0 负责人)Python (4,978 star) (1,059 fork)batch import
False Negative 🦋Good first issueHacktoberfestNeeds decision :lock:

描述

Current problem

C1802 currently catches this

Examples 1&2 (currently caught by rule C1802)

fruits = ["orange", "apple"]
vegetables = []

if len(fruits):
    print(fruits)

if not len(vegetables):
    print(vegetables)

I come across the following sometimes as well (potentially in botched attempt to fix the the flagged violation above), which I think should be equally flagged as a violation.

Examples 3&4 (not caught by PLC1802)

fruits = ["orange", "apple"]
vegetables = []

if len(fruits) > 0:
    print(fruits)

if len(vegetables) == 0:
    print(vegetables)

Examples 5&6 (recommended formulation)

fruits = ["orange", "apple"]
vegetables = []

if fruits:
    print(fruits)

if not vegetables:
    print(vegetables)

Desired solution

Examples 3&4 to be flagged as well

Additional context

See our previous discussion on this issue.

贡献者指南

技术栈
python
领域
toolingdeveloper experience
议题类型
feature
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
3
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
1-2 days
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
active
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
Pythonpylint internalsAST knowledge
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
45
研究方向
The issue requests extending the existing rule C1802 (use implicit booleaness not len) to also flag cases like `len(iterable) > 0` and `len(iterable) == 0`. Start by examining the current implementation of the checker in pylint's source code, likely in the `checkers/` directory. Review the referenced discussion at https://github.com/astral sh/ruff/issues/16798#issuecomment 2729812152 for additional context. The solution involves adding AST pattern matching for these additional patterns in the rule's logic, similar to how the existing `len()` usage is detected.