pandas: merge on column of collections.Counter (or even just dict) objects?

Question

I need to perform a merge of two pandas DataFrames using columns with collections.Counter objects (https://docs.python.org/2/library/collections.html#collections.Co

Answer 1

One way of getting around this is to create a column (for each DataFrame) of a version of your original data structure converted to a hashable type.

E.g.,

a['IDHash'] = a.ID.apply(lambda r: tuple(sorted(r.iteritems())))
b['IDHash'] = b.ID.apply(lambda r: tuple(sorted(r.iteritems())))

and then

pd.merge(a, b, on='IDHash')

After that, just erase the columns.