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# mellea.stdlib.requirements.python_reqs

> Requirements for Python code generation validation.

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Requirements for Python code generation validation.

## Classes

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### <span className="ml-2 inline-flex items-center rounded-full px-2 py-1 text-[0.7rem] font-bold tracking-wide bg-[#4ADE8033]/20 text-[#15803D]">CLASS</span> `PythonExecutionReq` <sup><a href="https://github.com/generative-computing/mellea/blob/v0.7.0.dev0/mellea/stdlib/requirements/python_reqs.py#L162" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Verifies that Python code runs without raising exceptions.

Optionally validates that captured stdout does not exceed a size limit,
eliminating the double-execution cost of separate OutputSizeLimit checks.

Extracts the highest-scoring Python code block from the model's last output
and validates or executes it according to the configured execution tier.

Use `execution_tier` to select behavior by intent:

* `"static"` (default) — parse and import-check only, no execution.
* `"local_unsafe"` — subprocess execution, no policy restrictions.
* `"local"` — subprocess execution with a declared capability policy.
* `"docker_unsafe"` — Docker-isolated execution, no policy restrictions.
* `"docker"` — Docker-isolated execution with a declared capability policy.

**Args:**

* `execution_tier`: One of `"static"`, `"local_unsafe"`, `"local"`,
  `"docker_unsafe"`, or `"docker"`.  Defaults to `"static"`.
* `policy`: Override the tier's default policy.
  Ignored for `"static"` and unsafe tiers unless explicitly provided.
* `allowed_imports`: Allowlist of importable top-level
  modules.  `None` allows any import.
* `max_output_chars`: Maximum allowed stdout size in characters.
  None = no size check (default). When set, adds output size validation
  in the same execution pass, avoiding the double-execution cost of using
  OutputSizeLimit. Only enforced for tiers that execute code (local\_unsafe,
  local, docker\_unsafe, docker); static tier skips output check.
* `timeout`: Deprecated.  Pass `policy=CapabilityPolicy(timeout=N)`
  instead.  When provided, overrides the policy timeout.
* `allow_unsafe_execution`: Deprecated.  Use
  `execution_tier="local_unsafe"` instead.
* `use_sandbox`: Deprecated.  Use `execution_tier="docker"` instead.

**Attributes:**

* `validation_fn`: The validation
  function attached to this requirement; always non-`None`.

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