# mypy Hacker Approved page: https://hackerapproved.com/p/mypy/ 28 people recommended mypy in Hacker News comments, 4 had mixed feelings and 13 criticized it, November 2025 to October 2026. It was recommended in 7 of 12 months, in 20 threads. It meets the Hacker Approved badge rule. **Verdict:** Free Python type checker people run in strict mode to catch bugs and keep large or AI-written code honest; critics say it is slow and lenient by default. Summary written by Claude from 48 comments. It was written before the November 2026 recount, and 45 of those comments still count. ## Why people recommend it - Helps AI coding agents stay honest (4 comments in the sample): "With agents it is helpful to make them run ruff and mypy to keep them honest" ([source](https://news.ycombinator.com/item?id=50174318)) "Use Mypy in strict mode and run it in the post-turn hook of your LLM harness" ([source](https://news.ycombinator.com/item?id=48105624)) "The one thing that did change anything was giving the agent a type checker." ([source](https://news.ycombinator.com/item?id=50257503)) - Strict mode catches real type errors (3 comments in the sample): "mypy doesn't see a problem by default; you need to enable strict mode." ([source](https://news.ycombinator.com/item?id=45942509)) "let mypy beat you up until the types are sound" ([source](https://news.ycombinator.com/item?id=46602579)) "Use pyright or mypy in strict mode." ([source](https://news.ycombinator.com/item?id=46705598)) - Keeps large Python projects manageable (3 comments in the sample): "Typing annotations + mypy can completely help you build and understand a complex system." ([source](https://news.ycombinator.com/item?id=48115801)) "Definitely mypy keeps my sanity in a relatively large Python project I'm working on" ([source](https://news.ycombinator.com/item?id=48845738)) "typing+mypy/mypyc goes a very long way" ([source](https://news.ycombinator.com/item?id=48870171)) - Precise, strong plugin support (2 comments in the sample): "It is still the most precise type checker, supports a lot of complicated cases and has plugins that make a lot of things more type…" ([source](https://news.ycombinator.com/item?id=46312823)) "For the most part I found mypy was able to infer more accurately and flexibly." ([source](https://news.ycombinator.com/item?id=46296714)) ## What people warn about - Misses bugs unless strict mode enabled (4 comments in the sample): "IDE extensions and mypy still miss some bugs which should never happen in typed languages." ([source](https://news.ycombinator.com/item?id=45838034)) "that will type check (at least with mypy) and now you lost safety" ([source](https://news.ycombinator.com/item?id=46857574)) "I've seen some truly simple things check out as ok in mypy" ([source](https://news.ycombinator.com/item?id=47410515)) - Slow on large codebases (3 comments in the sample): "It is dog slow as well as being the laziest of all, not catching many mistakes." ([source](https://news.ycombinator.com/item?id=48446726)) "the native implementations (mypy) are horribly slow at any meaningful size" ([source](https://news.ycombinator.com/item?id=48221645)) "mypy was taking >30s, which was not fast enough" ([source](https://news.ycombinator.com/item?id=46325777)) - Conflicts with pyright on dynamic code (1 comment in the sample): "there's still often (not always) fighting with typing, mypy, pyright because of the dynamic nature you mention" ([source](https://news.ycombinator.com/item?id=48838289)) ## Other Python type checkers people recommend - [ty Python type checker](https://hackerapproved.com/p/ty/): 60 recommend, 12 mixed, 23 criticize - [Pyright](https://hackerapproved.com/p/pyright/): 24 recommend, 6 mixed, 14 criticize - [Pyrefly](https://hackerapproved.com/p/pyrefly/): 22 recommend, 2 mixed, 8 criticize - [basedpyright](https://hackerapproved.com/p/basedpyright/): 9 recommend, 0 mixed, 7 criticize ## The badge A product earns the Hacker Approved badge when at least 10 people recommend it, recommenders outnumber critics at least 2 to 1 (mixed feelings count toward neither side), it was recommended in at least 4 of the 12 months and in at least 5 different threads, and no single thread supplies more than half of the people who recommend it. Health and money products are never badged. ## Cite as Hacker Approved, "mypy", https://hackerapproved.com/p/mypy/ (28 recommend, 4 mixed, 13 criticize; Hacker News comments, November 2025 to October 2026). Counts updated 3 Nov 2026, with data through October 31, 2026.