I haven't test it, just pythonic feeling of syntax. Think that the patch does not look bad, I found just minor issues.
+ flavors, counts = zip(*db.coffee_flavors_history(uid))
I like tuple here but it's not used anywhere in the code, so lets keep it consistent.
+ ax.pie(counts, autopct=lambda p: '{:.0f}'.format(p * sum(counts)/100) if p != 0 else '') Yes, I don't like lines *not wrapped* to 80 characters. Suggest at least new line after `... p:` - it helps with the readability also.
+ res = list(c.execute(""" + select f.name, count(c.flavor) from + (select num,date('now', 'localtime', -num || ' days') as d from days) ds
Again this wrapping (sorry). Also, for the first view, the query doesn't look nice. Guess that db queries can't be written nicely... jiri