memory leak

I have noticed a memory leak when using pylab.pcolor. Here is the code,
fa() and fb() do the same thing. The difference is the size of the array
which is passed to pcolor. With a large array pcolor leaks but not with a
small one.

import numpy as np
import matplotlib
from matplotlib import pylab
def fa():
    """ This function leaks.
    a = np.arange(1024**2)
    a = a.reshape(1024,1024)
    for i in range(1):
def fb():
    """This function does not leak.
    b = np.arange(1024)
    b = b.reshape(32,32)
    for i in range(1024):