svg diagrams using python

Try using matplotlib. You can configure it with a SVG backend.

pyCairo is an option worth looking at.

As you're looking for simple line graphics, probably, CairoPlot will fit your needs as it can generate svg output files out of the box. Take a look at this.

This example image shows only a few of its capabilities. Using the trunk version available at launchpad you'll be able to add a legend box and add axis titles.

Besides that, using the trunk version, it's possible to generate:

• DotLine charts (the ones I believe you need)
• Scatter charts
• Pie/Donut charts
• Horizontal/Vertical Bar charts
• Gantt charts