pytest-dev/pytest · error · UsageError

: config option ' ' expects a float, got

Error message

{self.inipath}: config option '{name}' expects a float, got {value_type}: {value!r}

What it means

Raised by pytest's TOML config parser when a 'float'-type ini option receives a non-numeric value. Integers are accepted (since int is in the accepted tuple), but booleans are explicitly rejected via `isinstance(value, bool)`. Strings are rejected.

Solutions

Use an unquoted number: change `timeout = "60"` to `timeout = 60.0` or `timeout = 60`
Replace true/false with the intended numeric value
Ensure the value is a literal float or int, not a string expression

Example fix

// pyproject.toml — before
[tool.pytest.ini_options]
timeout = "60"

// after
[tool.pytest.ini_options]
timeout = 60.0

Defensive patterns

Strategy: validation

Validate before calling

import tomllib
with open('pyproject.toml', 'rb') as f:
    data = tomllib.load(f)
opts = data.get('tool', {}).get('pytest', {}).get('ini_options', {})
for key, val in opts.items():
    if isinstance(val, str):
        print(f"{key}: got string {val!r}, consider unquoted number if type is 'float'")
    elif isinstance(val, bool):
        print(f"{key}: got bool, but float type rejects bool")

Type guard

def is_toml_number_not_bool(value: object) -> bool:
    return isinstance(value, (int, float)) and not isinstance(value, bool)

Prevention

Use unquoted numeric literals for float options
Remember both int and float literals are accepted for float type, but bool is not
Never quote numbers in TOML

When it happens

Trigger: An addini(type='float') option is set to a string or bool in pyproject.toml. Example: timeout = "60" (string) or timeout = true (bool) instead of timeout = 60.0 or timeout = 60. The check `not isinstance(value, (float, int)) or isinstance(value, bool)` triggers.

Common situations: Quoting a float (making it a string). Using true/false (bool) for a threshold. Assuming TOML coerces strings to numbers (it does not).

Related errors

AI-assisted analysis of pytest-dev/pytest@0d6fbdeffa (2026-08-11). Data as JSON: /api/errors/6671456ff48e7755. Report an issue: GitHub.

Appendix: source

Thrown at src/_pytest/config/__init__.py:2012

            # Expect a boolean.
            if not isinstance(value, bool):
                raise TypeError(
                    f"{self.inipath}: config option '{name}' expects a bool, "
                    f"got {value_type}: {value!r}"
                )
            return value
        elif type == "int":
            # Expect an integer (but not bool, which is a subclass of int).
            if not isinstance(value, int) or isinstance(value, bool):
                raise TypeError(
                    f"{self.inipath}: config option '{name}' expects an int, "
                    f"got {value_type}: {value!r}"
                )
            return value
        elif type == "float":
            # Expect a float or integer only.
            if not isinstance(value, (float, int)) or isinstance(value, bool):
                raise TypeError(
                    f"{self.inipath}: config option '{name}' expects a float, "
                    f"got {value_type}: {value!r}"
                )
            return value
        elif type == "string":
            # Expect a string.
            if not isinstance(value, str):
                raise TypeError(
                    f"{self.inipath}: config option '{name}' expects a string, "
                    f"got {value_type}: {value!r}"
                )
            return value
        else:
            return self._getini_unknown_type(name, type, value)

    def _getconftest_pathlist(
        self, name: str, path: pathlib.Path
    ) -> list[pathlib.Path] | None:

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