You can’t. A list is a mutable, variable length structure. If you need a fixed-length structure, use a tuple instead:
Tuple[float, float, float, float, float, float, float, float, float, float]
Or better still, use a named tuple, which has both indices and named attributes:
class BunchOfFloats(NamedTuple):
foo: float
bar: float
baz: float
spam: float
ham: float
eggs: float
monty: float
python: float
idle: float
cleese: float
A list is simply the wrong data type for a fixed-length data structure.