SeleniumHQ/selenium · error · TypeError

service_args must be a sequence

Error message

service_args must be a sequence

What it means

Raised as TypeError by the InternetExplorerService.service_args setter when the value is a bare str or not a Sequence type. Identical to the Firefox service_args validation: a str is explicitly rejected (even though str is a Sequence) because it would be unpacked into individual characters. The value must be a list/tuple of string arguments.

Source

Thrown at py/selenium/webdriver/ie/service.py:95

            executable_path=executable_path,
            port=port,
            log_output=log_output,
            driver_path_env_key=driver_path_env_key,
            **kwargs,
        )

    def command_line_args(self) -> list[str]:
        return [f"--port={self.port}"] + self._service_args

    @property
    def service_args(self) -> Sequence[str]:
        """Returns the sequence of service arguments."""
        return self._service_args

    @service_args.setter
    def service_args(self, value: Sequence[str]):
        if isinstance(value, str) or not isinstance(value, Sequence):
            raise TypeError("service_args must be a sequence")
        self._service_args = list(value)

View on GitHub (pinned to aa36b38e69)

Solutions

1. Wrap arguments in a list: service_args=['--verbose']
2. Use shlex.split() to split a string into a proper argument list
3. Pass a tuple of argument strings

Example fix

// before
service = Service(service_args='--log-level=TRACE')

// after
service = Service(service_args=['--log-level=TRACE'])

args = '--log-level=TRACE'
if isinstance(args, str):
    args = [args]
service = Service(service_args=args)

from collections.abc import Sequence
def is_arg_sequence(v) -> bool:
    return not isinstance(v, str) and isinstance(v, Sequence)

try:
    service.service_args = args
except TypeError:
    service.service_args = [args] if isinstance(args, str) else list(args)

When it happens

Trigger: Passing service_args='--verbose' (single string) or service_args=123 (non-sequence) triggers the TypeError. Only list or tuple of strings is accepted.

Common situations: Developers passing a single CLI flag as a string. Passing a space-delimited string expecting automatic splitting.

Related errors

• service_args must be a sequence
• service_args must be a sequence
• {self.name} should be of type {self.expected_type.__name__}
• reuse must be a boolean
• service_args must be a sequence

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/34e7c444f0f13f17. Report an issue: GitHub.