Using pyDatalog to perform a data join

meatlog.py

from pyDatalog import pyDatalog as pdl

# set up some basic terms
pdl.create_terms('F,G,Q,what,eat')
#      F         G
+what('pork', 'meat')
+what('lamb', 'meat')
+what('peas', 'veg')
+what('beans', 'veg')

#     F       Q
+eat('pork', 3)
+eat('lamb', 4)
+eat('peas', 2)
+eat('beans', 1)

# set up the relationships
pdl.create_terms('geat,sumg,qtys')
geat(G, Q) <= (what(F, G) & eat(F, Q))
(sumg[G] == sum_(Q, for_each = G)) <= geat(G, Q)
qtys(G, Q) <= (sumg[G] == Q)


# Now onto the crucial question: how much of each food group did I eat?
print(qtys(G, Q))

# If we want to manipulate the data in vanilla Python
result = qtys(G, Q).data
print(result)

Discussion about the code is available here:
https://mcturra2000.wordpress.com/2015/12/11/using-pydatalog-to-join-data-simply/