Joining all rows of a CSV file that have the same 1st column value in Python

Question

I have a CSV file that goes something like this:

[\'Name1\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\', \'\',

Answer 1

You should use itertools.groupby:

t = [ 
['Name1', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '+'],
['Name1', '', '', '', '', '', 'b', '', '', '', '', '', '', '', '', '', '', '', '', '', ''],
['Name2', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', 'a', ''],
['Name3', '', '', '', '', '+', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''] 
]

from itertools import groupby

# TODO: if you need to speed things up you can use operator.itemgetter
# for both sorting and grouping
for name, rows in groupby(sorted(t), lambda x:x[0]):
    print join_rows(rows)

It's obvious that you'd implement the merging in a separate function. For example like this:

def join_rows(rows):
    def join_tuple(tup):
        for x in tup:
            if x: 
                return x
        else:
            return ''
    return [join_tuple(x) for x in zip(*rows)]