Loop-help for a newbie?

[buran]

in perfringo's code you have

for pair in cols

in each iteration pair will be 2-elemt tuple, e.g. ('B', 'C')
0 and 1 refer to index of each element, i.e. pair[0] is 'B' and pair[1] is 'C'.

Compare it to my code where I used col1, and col2 to unpack the tuple directly in two variables, instead of using one variable that is container and use index to access its elements