Convert a String Into a Float From List In Python

You might write a function that will convert the strings according to whatever rules you want, and then map it over the list:

from typing import Union

def convert_string(x: str) -> Union[str, int, float]:
    """Attempts to convert a string to an int or float.
    Returns the string unchanged if no conversion possible."""
    try:
        return int(x)
    except ValueError:
        pass
    try:
        return float(x)
    except ValueError:
        return x

>>> list(map(convert_string, ["foo", "1.21", "1"]))
['foo', 1.21, 1]

Practically speaking, I think it'd be better to group these values, perhaps into a NamedTuple?

>>> from typing import List, NamedTuple
>>> class Thingy(NamedTuple):
...     date: str
...     type: str
...     num1: float
...     num2: float
...
>>> def build_thingy(elements: List[str]) -> Thingy:
...     """Build a Thingy from input list of 4 elements.
...     Raises if the input list is not valid."""
...     [date, type, num1, num2] = elements
...     return Thingy(date, type, float(num1), float(num2))
...
>>> [build_thingy(List1[i:i+4]) for i in range(0, len(List1), 4)]
[Thingy(date='01/01/2020', type='AType', num1=4.3, num2=789.33),
 Thingy(date='02/01/2020', type='BType', num1=342.77, num2=84.0),
 Thingy(date='03/01/2020', type='CType', num1=2.0, num2=245.22)]