Question

I’ve got a list like
[(1, 2), (1, 8), (2, 3), (2, 7), (2, 8), (2, 9), (3, 1), (3, 2), (3, 5), (3, 6), (3, 7), (3, 7), (3, 9)]

I want to make it looks like
[(‘1′,’ ‘, ‘2’, ‘8’), (‘2’, ‘ ‘, ‘3’, ‘7’, ‘8’, ‘9’), (‘3’, ” “, ‘2’, ‘5’, ‘6’, ‘7’, ‘7’, ‘9’)]

How can I code this loop? Really tried times, and nothing came up. Please help~~

Answer 1

a = [(1, 2), (1, 8), (2, 3), (2, 7), (2, 8), (2, 9), (3, 1), (3, 2), (3, 5), (3, 6),  (3, 7), (3, 7), (3, 9)]

x1=None  # here we keep track of the last x we saw
ys=None  # here we keep track of all ys we've seen for this x1

result = [] 

for x,y in a:
    if x != x1:  # this is an x we haven't seen before
        if ys:   # do we have results for the last x?
            result.append( ys ) 
        ys = [ x, '', y ] # initialize the next set of results
        x1 = x
    else:
        ys.append( y ) # add this to the results we are buliding

if ys:
    result.append( ys )  # add the last set of results

print result