When reasoning about how PyCharm should infer a type or whether something ought to be a type error, cross-checking against the real third-party checkers is the fastest way to gain insight — and to see where they disagree. This skill runs them all on a scratch file or snippet and collates the output into a single report.
Run it
${CLAUDE_SKILL_DIR}/scripts/compare_typecheckers.py invokes each checker
through uvx (fetched on demand — no install; the network is used on first run)
and prints a Markdown report: a summary table (exit code / verdict / timing per
tool) followed by each tool's raw output.
# Inline snippet:
uv run ${CLAUDE_SKILL_DIR}/scripts/compare_typecheckers.py -c 'def f(x: int) -> int:
return x
f("a")'
An existing file:uv run ${CLAUDE_SKILL_DIR}/scripts/compare_typecheckers.py path/to/test.py
A subset, written to a file:uv run ${CLAUDE_SKILL_DIR}/scripts/compare_typecheckers.py test.py --tools ty,mypy -o /tmp/report.md
Flags: `-c/--code` (inline snippet), `-t/--tools ty,mypy,…` (subset), `-o/--output`
(write to file), `--timeout` (per-checker seconds, default 180). The script exits
0 whenever it produced a report — findings live in the report, not the exit code.
## Reading the result
- The summary table shows each tool's exit code (**0 = nothing flagged**,
non-zero = the checker reported an issue or failed to run), a verdict, and time.
- Output **formats differ** per tool, so read each section, not just the table:
- `ty` (Astral) and `pyrefly` (Meta) each have their own diagnostic style.
- `basedpyright` is pyright-based and also emits extra diagnostics such as
`reportUnusedCallResult`.
- `mypy` and `zuban` share the same message format (`zuban` is mypy-compatible).
- The checkers track their latest releases through `uvx`, so behaviour can shift
over time — record the date when capturing results in a YouTrack issue or test.
## Manual one-offs
The exact per-tool invocations, if you want to run just one by hand (note
`basedpyright` takes the file positionally — no `check` subcommand):
| Tool | Command |
|------|---------|
| ty | `uvx ty check test.py` |
| pyrefly | `uvx pyrefly check test.py` |
| basedpyright | `uvx basedpyright test.py` |
| mypy | `uvx mypy test.py` |
| zuban | `uvx zuban check test.py` |