x-axis line in bar plots


I am creating a bar graph which contains negative values on y-axis.
Everything is fine, but there is no line corresponding to y=0, so the
bars seem a bit weird. Here is a short example-

x = range(10)
y = [random.randint(-10, 10) for i in x]
bar(x, y)

What I want is a line to be drawn at y=0. Any idea how to get it done?
Apologies if this has been asked before. I searched but couldn't find
a way.