converting the difference in vectors to between 0 and 1

Read about the Dot product In general The dot product of 2 vectors is equal the cosine of the angle between the 2 vectors multiplied by the magnitude (length) of both vectors.

dot( A, B ) == | A | * | B | * cos( angle_A_B ) 

This follows, that the dot product of 2 unit vectors is equal the cosine of the angle between the 2 vectors, because the length of a unit vector is 1.

uA = normalize( A )
uB = normalize( B )
cos( angle_A_B ) == dot( uA, uB )

If 2 normalized vectors point in the same direction, then the dot product is 1, if the point in the opposite direction, the dot product is -1 and if the vectors are perpendicular then the dot product is 0.

In pygame the dot product can be computed by math.Vector2.dot(). If A and B are pygame.math.Vector2 objects:

uA = A.normalize()
uB = B.normalize()
AdotB = uA.dot(uB)

In the example above, AdotB is in range [-1.0, 1.0]. AdotB * 0.5 + 0.5 is in range [0.0, 1.0] and math.acos(AdotB) / math.pi + 1 maps the angle between A and B linearly to the range [0.0, 1.0].

Furthermore, pygame.math.Vector2.angle_to() calculates the angle to a given vector in degrees. A value in range [0.0, 2.0] dependent on the angle can be computed by

w = 1 - A.angle_to(B) / 180