Consider the dataframes left and right
left = pd.DataFrame([['a', 1], ['b', 2]], list('XY'), list('AB'))
left
   A  B
X  a  1
Y  b  2
right = pd.DataFrame([['a', 3], ['b', 4]], list('XY'), list('AC'))
right
   A  C
X  a  3
Y  b  4
join
Think of join as wanting to combine to dat...