PollyReports is a Python module that provides a set of classes for database report writing. It assumes that you are using Reportlab to do PDF generation, but can work with any "canvas-like" object as desired.
PollyReports provides the following framework for report generation:
A Report object has a data source bound to it at instantiation. One or more Band objects (at least, a detail Band) must be added to it, and then the generate() method will be called to process the data source. The data source must be an iterator that produces objects that can be accessed via  operations, meaning mainly dict, list, and tuple types, i.e. the most common types of records returned by standard database modules. The detail band is generated() once for each row.
Band objects contain a list of Elements (generally at least one) which define how data from the row should be printed. An Element may print any normal data item or label and may be subclassed to handle other things like images. Generating a band in turn calls Element.generate() for each element, producing a list of Renderers with the first item in the list being the overall height of the band. The height is used to decide if the band will fit on the current page; if not, a new page will be created first. When the page is finally ready for the band, Renderer.render() will be called for each Renderer in the element list in order to actually render the data.
This version is written for Python 2.7, but should be easily adapted to Python 3.