Class Bytes

traitlets/traitlets.py:2867–2897

A trait for byte strings.

# for Python 3 conversion and for reliable unicode behaviour on Python 2. So
# we don't have a Str type.
class Bytes(TraitType[bytes, bytes]):
    """A trait for byte strings."""

    default_value = b""
    info_text = "a bytes object"

    def validate(self, obj: t.Any, value: t.Any) -> bytes | None:
        if isinstance(value, bytes):
            return value
        self.error(obj, value)

    def from_string(self, s: str) -> bytes | None:
        if self.allow_none and s == "None":
            return None
        if len(s) >= 3:
            # handle deprecated b"string"
            for quote in ('"', "'"):
                if s[:2] == f"b{quote}" and s[-1] == quote:
                    old_s = s
                    s = s[2:-1]
                    warn(
                        "Supporting extra quotes around Bytes is deprecated in traitlets 5.0. "
                        f"Use {s!r} instead of {old_s!r}.",
                        DeprecationWarning,
                        stacklevel=2,
                    )
                    break
        return s.encode("utf8")

    def subclass_init(self, cls: type[t.Any]) -> None:
        pass  # fully opt out of instance_init


class CBytes(Bytes, TraitType[bytes, t.Any]):