Python rational number to binary converter

Question

I made a rational number- binary converter for positive numbers, but how do I do it for rational numbers?

# Python3 program to convert a
# decimal number to binary number
 
# function to convert
# decimal to binary
def decToBinary(n):
     
    # array to store
    # binary number
    binaryNum = [0] * n
 
    # counter for binary array
    i = 0;
    while (n > 0):
 
        # storing remainder
        # in binary array
        binaryNum[i] = n % 2
        n = int(n / 2)
        i += 1
 
    # printing binary array
    # in reverse order
    for j in range(i - 1, -1, -1):
        print(binaryNum[j], end = "")
 
# Driver Code
n = 17;
decToBinary(n)

I made a rational number- binary converter for positive numbers, but how do I do it for rational numbers?