How to plot data against specific dates on the x-axis using matplotlib

I have a dataset consisting of date-value pairs. I want to plot them in a bar graph with the specific dates in the x-axis.

My problem is that matplotlib distributes the xticks over the entire date range; and also plots the data using points.

The dates are all datetime objects. Here's a sample of the dataset:

data = [(DT.datetime.strptime('2010-02-05', "%Y-%m-%d"), 123),
        (DT.datetime.strptime('2010-02-19', "%Y-%m-%d"), 678),
        (DT.datetime.strptime('2010-03-05', "%Y-%m-%d"), 987),
        (DT.datetime.strptime('2010-03-19', "%Y-%m-%d"), 345)]

Here is a runnable code sample using pyplot

import datetime as DT
from matplotlib import pyplot as plt

data = [(DT.datetime.strptime('2010-02-05', "%Y-%m-%d"), 123),
        (DT.datetime.strptime('2010-02-19', "%Y-%m-%d"), 678),
        (DT.datetime.strptime('2010-03-05', "%Y-%m-%d"), 987),
        (DT.datetime.strptime('2010-03-19', "%Y-%m-%d"), 345)]

x = [date for (date, value) in data]
y = [value for (date, value) in data]

fig = plt.figure()

graph = fig.add_subplot(111)
graph.plot_date(x,y)

plt.show()

QUESTION SUMMARY:
My situation is more like I have an Axes instance ready (referenced by graph in the code above) and I want to do the following:

1. Make the xticks correspond to the exact date values. I have heard of matplotlib.dates.DateLocator but I have no idea how create one and then associate it with a specific Axes object.
2. Get tighter control over the type of graph being used (bar, line, points, etc.)