The MongoDB aggregation framework provides a means to calculate aggregated values without having to use map-reduce. While map-reduce is powerful, it is often more difficult than necessary for many simple aggregation tasks, such as totaling or averaging field values.
See how to use the build-in data-aggregation-pipelines for averages, summation, grouping, reshaping. See how to work with documents, sub-documents, grouping by year, month, day, etc.
This talk will give many (live) examples how to make the most of your data with pymongo with a few lines of code.
added 28/07/15: iPython notebook & sample data can be found in this git