import petl.interactive as etl

t1 = etl.wrap([['foo', 'bar'], [1, 'a'], [2, 'b']])
t1

t2 = etl.wrap([['foo', 'bar'], [1, 'a'], [2, 'c']])
t2

t3 = etl.merge(t1, t2, key='foo')
t3

t4 = (etl
    .cat(
        t1.addfield('source', 1),
        t2.addfield('source', 2)
    )
    .conflicts(key='foo', exclude='source')
)
t4