How can I create this type hint.

[deanhystad]

I am trying to create a type string using type hint information I get using inspect.signature(). I have this working for most types:

Output:
Type        Type String
----        -----------
int         "I"
float       "F"
str         "S"
list[int]   ">II"
list[float] ">IF"

My problem is that I actually have two list types that differ by "direction": TO and FROM. A TO list is used to pass values from a sender to a receiver. A FROM list is used to return values from the receiver back to the sender. TO and FROM lists are part of a messaging protocol that was originally used to communicate between C programs.

example receiver:
function(to_size, to_values, from_size, from_values)
{
    for(int i = 0; i < MIN(to_size, from_size); i++)
        from_values[i] = to_values[i];
}

example sender:
int *to_values = {1, 2, 3, 4};
int *from_values[4];
typestr = remote.typestring("function")  // returns ">II<II"
remote.call("function", typestr, 4, to_values, 4, from_values)

I still need to communicate to and between C programs, plus there is much legacy code that uses this protocol. Changes to the protocol is off the table unless they are backward compatible. I need help making a type hint that will let me write something like this in Python

# example receiver
function(to_values: list[int], from_values: return_list[int]):
    for i in range(min(len(to_values), len(from_values))):
        from_values[i] = to_values[i]

# example sender
to_values = [1, 2, 3, 4]
from_values = numpy.zeros(4, int32)
typestr = remote.typestring("function")
remote.call("function", typestr, to_values, 4, from_values)

# and the calling mechanism will expand to
remote.call("function", typestr, len(to_values), to_values, len(from_values), from_values)