This is my first try:

ddata = {}

inside_matrix = False for row in file("data.txt"): if row.strip(): fields = row.split() if len(fields) == 2: inside_matrix = False ddata[fields[0]] = [fields[1]] lastkey = fields[0] else: if inside_matrix: ddata[lastkey][1].append(fields) else: ddata[lastkey].append([fields]) inside_matrix = True

# This gives some output for testing only: for k in sorted(ddata): print k, ddata[k]

Input file data.txt:

key1 value1 key2 value2 key3 value3

key4 value4 spec11 spec12 spec13 spec14 spec21 spec22 spec23 spec24 spec31 spec32 spec33 spec34

key5 value5 key6 value6

key7 value7 more11 more12 more13 more21 more22 more23

key8 value8

The output:

key1 ['value1'] key2 ['value2'] key3 ['value3'] key4 ['value4', [['spec11', 'spec12', 'spec13', 'spec14'], ['spec21', 'spec22', 'spec23', 'spec24'], ['spec31', 'spec32', 'spec33', 'spec34']]] key5 ['value5'] key6 ['value6'] key7 ['value7', [['more11', 'more12', 'more13'], ['more21', 'more22', 'more23']]] key8 ['value8']

If there are many simple keys, then you can avoid creating a single element list for them, but then you have to tell apart the two cases on the base of the key (while now the presence of the second element is able to tell apart the two situations). You can also use two different dicts to keep the two different kinds of data.

Bye, bearophile