Let’s say you have something like this:

alRemapFloat
{
 name alRemapFloat1
 input alCombineColor1.r
}

where the R component of the alCombineColor node is linked to the alRemapFloat.input parameter.

To get the component that is linked to input, you use the comp parameter of AiNodeGetLink(), like so:

node = AiNodeLookUpByName( "alRemapFloat1" )

comp = c_int()
linked_node = AiNodeGetLink( node, "input", comp);

Since R is connected, comp will be 0.

comp is -1 if the entire output is linked, or a number between 0 and 3 to indicate a specific component (0 for r, 1 for g, 2 for b, and 3 for a)

Note that you can pass a c_int to AiNodeGetLink(). ctypes takes care of converting it to a byref() for you.