Check if two ranges intersect

ranges_intersect.py

# Check overlap of range [a1, a2) and range [b1, b2), where None indicates infinity.
def ranges_intersect(a, b):
    # Make sure that a starts before or at b.
    if b[0] is None or (a[0] is not None and b[0] < a[0]):
        a, b = b, a
        
    # If b starts before a ends, then there is an intersection.
    return b[0] is None or a[1] is None or b[0] < a[1]