A Python counter. Using it for colour incrementing.

class z:

    """Counter.  My first!  

    Instantiate with number of items between 0 and 1.

    Calling the class will return an incrementing value.

    """

    def __init__(self, n):

        self.n = n

        self.i = -1

    def __call__(self):

        """This gets called when the instantiated object is called"""

        if self.i == self.n:

            raise StopIteration

        self.i += 1

        return self.i * 1.0 / (self.n - 1)

Use as,

In [1]:  a = z(10)

In [2]:  print a(), a(), a(), a(), a(), a(), a(), a(), a(), a()

         0.0 0.111 0.222 0.333 0.444 0.555 0.666 0.777 0.888 1.0

(Those results are truncated ;) )

Use to control colour as,

from matplotlib import cm
a = z(10)
plot(x, y, color=cm.jet(a))
plot(x2, y2, color=cm.jet(a))
plot(x3, y3, color=cm.jet(a))