Convert dictionary of lists of tuples to list of lists/tuples in python

I've got dictionary of lists of tuples. Each tuple has timestamp as first element and values in others. Timestamps could be different for other keys:

dict = {
            'p2': [(1355150022, 3.82), (1355150088, 4.24), (1355150154, 3.94), (1355150216, 3.87), (1355150287, 6.66)],
            'p1': [(1355150040, 7.9), (1355150110, 8.03), (1355150172, 8.41), (1355150234, 7.77)],
            'p3': [(1355150021, 1.82), (1355150082, 2.24), (1355150153, 3.33), (1355150217, 7.77), (1355150286, 6.66)],
}

I want this convert to list of lists:

ret = [
            ['time', 'p1', 'p2', 'p3'],
            [1355149980, '', 3.82, 1.82],
            [1355150040, 7.9, 4.24, 2.24],
            [1355150100, 8.03, 3.94, 3.33],
            [1355150160, 8.41, 3.87, 7.77],
            [1355150220, 7.77, '', ''],
            [1355150280, '', 6.66, 6.66]
]

I'm making conversion with that dirty definition:

def convert_parameters_dict(dict):
    tmp = {}
    for p in dict.keys():
        for l in dict[p]:
            t = l[0] - l[0] % 60
            try:
                tmp[t][p] = l[1]
            except KeyError:
                tmp[t] = {}
                tmp[t][p] = l[1]
    ret = []
    ret.append([ "time" ] + sorted(dict.keys()))
    for t, d in sorted(tmp.iteritems()):
        l = []
        for p in sorted(dict.keys()):
            try:
                l.append(d[p])
            except KeyError:
                l.append('')
        ret.append([t] + l)
    return ret

Maybe there is some much prettier way?

Have a look at pandas:

import pandas as pd

d = {
            'p2': [(1355150022, 3.82), (1355150088, 4.24), (1355150154, 3.94), (1355150216, 3.87), (1355150287, 6.66)],
            'p1': [(1355150040, 7.9), (1355150110, 8.03), (1355150172, 8.41), (1355150234, 7.77)],
            'p3': [(1355150021, 1.82), (1355150082, 2.24), (1355150153, 3.33), (1355150217, 7.77), (1355150286, 6.66)],
} 

ret = pd.DataFrame({k:pd.Series({a-a%60:b for a,b in v}) for k,v in d.iteritems()})

returns

p1    p2    p3
1355149980   NaN  3.82  1.82
1355150040  7.90  4.24  2.24
1355150100  8.03  3.94  3.33
1355150160  8.41  3.87  7.77
1355150220  7.77   NaN   NaN
1355150280   NaN  6.66  6.66

It is not a list of lists, but using pandas you can do much more with this data (such as convert the unix timestamps to datetime objects with a single command).

StackExchange Code Review Q#19572, answer score: 7