You didn't mention what output format you need but reportlab is good at creating charts both in pdf and bitmap (e.g. png) format.
Here is a simple example of a barchart in png and pdf format:
from reportlab.graphics.shapes import Drawing
from reportlab.graphics.charts.barcharts import VerticalBarChart
d = Drawing(300, 200)
chart = VerticalBarChart()
chart.width = 260
chart.height = 160
chart.x = 20
chart.y = 20
chart.data = [[1,2], [3,4]]
chart.categoryAxis.categoryNames = ['foo', 'bar']
chart.valueAxis.valueMin = 0
d.add(chart)
d.save(fnRoot='test', formats=['png', 'pdf'])
alt text http://i40.tinypic.com/2j677tl.jpg
Note: the image has been converted to jpg by the image host.