Moving window for a nested python list

list_moving_window.py

# Test fixture for lineStrings
lineStrings = [(i, "obj{0}".format(i),) for i in range(1011)]

stepSize = 200
nSteps = len(lineStrings)/stepSize

print "there are {0} objs in lineStrings".format(len(lineStrings))
steps = range(0, nSteps+1)
for stepI in steps:
    # Get the first object in the window
    firstObj_i = stepSize*stepI
    firstObj = lineStrings[firstObj_i]

    # Get the next object
    try:
        nextObj_i = stepSize*(steps[stepI+1])-1
        nextObj = lineStrings[nextObj_i]
    except IndexError:
        nextObj = lineStrings[-1]

    print "firstObj: {0}\t\tnextObj: {1}".format(firstObj, nextObj)