pytest-dev/pytest · error · TypeError

{self.inipath}: config option '{name}' expects a list of str

Error message

{self.inipath}: config option '{name}' expects a list of strings, but item at index {i} is {item_type}: {item!r}

What it means

Raised by Config._getini_toml (config/__init__.py:1965-1971) for a 'paths'-typed option in TOML mode when the value IS a list but at least one element is not a str. The message names the offending index, item type, and value to pinpoint the bad entry.

Source

Thrown at src/_pytest/config/__init__.py:1968

        default: Any,
    ):
        """Handle TOML config values with strict type validation and no coercion.

        In TOML mode, values already have native types from TOML parsing.
        We validate types match expectations exactly, including list items.
        """
        value_type = builtins.type(value).__name__
        if type == "paths":
            # Expect a list of strings.
            if not isinstance(value, list):
                raise TypeError(
                    f"{self.inipath}: config option '{name}' expects a list for type 'paths', "
                    f"got {value_type}: {value!r}"
                )
            for i, item in enumerate(value):
                if not isinstance(item, str):
                    item_type = builtins.type(item).__name__
                    raise TypeError(
                        f"{self.inipath}: config option '{name}' expects a list of strings, "
                        f"but item at index {i} is {item_type}: {item!r}"
                    )
            dp = (
                self.inipath.parent
                if self.inipath is not None
                else self.invocation_params.dir
            )
            return [dp / x for x in value]
        elif type in {"args", "linelist"}:
            # Expect a list of strings.
            if not isinstance(value, list):
                raise TypeError(
                    f"{self.inipath}: config option '{name}' expects a list for type '{type}', "
                    f"got {value_type}: {value!r}"
                )
            for i, item in enumerate(value):
                if not isinstance(item, str):

View on GitHub (pinned to 98b357f69e)

Solutions

Ensure every element of the paths array is a quoted TOML string.
Use the reported index to find and fix the specific bad entry.
Remove any non-path elements (numbers/bools) from the array.

Example fix

# before (pyproject.toml)
testpaths = ["tests", 42]

# after
testpaths = ["tests", "tests_42"]

Defensive patterns

Strategy: validation

Validate before calling

def validate_paths_items(value):
    for i, item in enumerate(value):
        if not isinstance(item, str):
            raise TypeError(f'paths[{i}] must be str, got {type(item).__name__}')
    return value

Type guard

def all_items_str(value) -> bool:
    return isinstance(value, list) and all(isinstance(x, str) for x in value)

Try / catch

try:
    config.getini(name)
except Exception:
    # stringify/remove non-path entries and reload

Prevention

Quote every entry of TOML path arrays.
Avoid mixing types in a single array.
Use the reported index to locate the bad item quickly.

When it happens

Trigger: Supplying a TOML array for testpaths/pythonpath/norecursedirs where one element is an int, bool, or nested table, e.g. testpaths = ["tests", 42].

Common situations: Mixed-type arrays after a partial TOML edit; copy-paste from YAML/JSON leaving unquoted numerics; booleans (true/false) accidentally included as path entries.

Related errors

AI-assisted analysis of pytest-dev/pytest@98b357f69e (2026-08-04). Data as JSON: /data/errors/f5016b8dd772f962.json. Report an issue: GitHub.