I have just worked on something similar and used this thread as a starting point.
However, I stumbled upon a problem, that may be of interest for others as well:
When one actually has defined the svg dimensions in the svg file by using physical units, like inches or mm, the renderPDF.drawToFile method will interprete all those units as Points.
So if you want to do the conversion printer ready, meaning there will be no scaling needed during printing of the PDF, you can do it like this:
from svglib.svglib import svg2rlg
from reportlab.graphics import renderPDF
drawing = svg2rlg("file.svg")
scaleFactor = 1./0.3527
drawing.width *= scaleFactor
drawing.height *= scaleFactor
The scale factor above is from mm to Points. Just look up the factor you need, e.g. here: