Exception handling for a chain of prompts
The whole port and count thing is a total waste of time. If you were stuck with it:


port is redundant, as break is what actually ends the loop;
If port was being used (e.g. while port:) it should be a bool (True/False) rather than an int (1/0);
You shouldn't have whitespace around the = for default argument values (def inputin(count=1, port=0):);
The if conditions should have more space and fewer parentheses: if port == 0 and count == 3:; and
count+=-1 should be count -= 1. 


Only two of your inputs actually need to be numbers, yet you wrap the whole thing in try; that block should be as short as you can make it. You can factor out the integer inputs for much cleaner code (see e.g. Asking the user for input until they give a valid response). For the other three inputs the return from input is always a string, so the str calls are totally redundant. 

Compare:

def int_input(prompt):
    """Validate integer-only user input."""
    while True:
        try:
            return int(input(prompt))
        except ValueError:
            print("Please enter an integer.")

def input_in():
    """Get required user inputs."""
    background = input("Enter the background color: ")
    num_sides = int_input("Enter the number of sides: ")
    arm_len = int_input("Enter the length of each side: ")
    turtle_color = input("Enter the turtle color: ")
    turtle_shape = input("Enter the turtle shape: ")
    ...


Note the adherence to the style guide and use of docstrings to explain what each function does. 

As additional exercises:


Add limits to the integer validation, allowing a minimum and maximum to be set for the function (a negative arm_len wouldn't make much sense, for example);
Create a color_input function to validate the user's color selection, and use it where appropriate; and
Create a shape_input function to do the same for shapes.